diff --git a/.gitattributes b/.gitattributes
index a549b49f237..da26ae4167d 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -2425,7 +2425,6 @@ src/mame/includes/mw8080bw.h svneol=native#text/plain
 src/mame/includes/mystston.h svneol=native#text/plain
 src/mame/includes/n64.h svneol=native#text/plain
 src/mame/includes/n8080.h svneol=native#text/plain
-src/mame/includes/nam_cust.h svneol=native#text/plain
 src/mame/includes/namcoic.h svneol=native#text/plain
 src/mame/includes/namcona1.h svneol=native#text/plain
 src/mame/includes/namconb1.h svneol=native#text/plain
@@ -2773,6 +2772,10 @@ src/mame/machine/mw8080bw.c svneol=native#text/plain
 src/mame/machine/n64.c svneol=native#text/plain
 src/mame/machine/namco50.c svneol=native#text/plain
 src/mame/machine/namco50.h svneol=native#text/plain
+src/mame/machine/namco51.c svneol=native#text/plain
+src/mame/machine/namco51.h svneol=native#text/plain
+src/mame/machine/namco53.c svneol=native#text/plain
+src/mame/machine/namco53.h svneol=native#text/plain
 src/mame/machine/namcoio.c svneol=native#text/plain
 src/mame/machine/namcoio.h svneol=native#text/plain
 src/mame/machine/namcond1.c svneol=native#text/plain
diff --git a/src/emu/sound/namco52.c b/src/emu/sound/namco52.c
index 41859b53fb5..2a603af4092 100644
--- a/src/emu/sound/namco52.c
+++ b/src/emu/sound/namco52.c
@@ -2,7 +2,7 @@
 
 Namco 52XX
 
-This instance of the Fujitsu MB8852 MCU is programmed to act as a sample player.
+This instance of the Fujitsu MB8843 MCU is programmed to act as a sample player.
 It is used by just two games: Bosconian and Pole Position.
 
 A0-A15 = address to read from sample ROMs
@@ -180,7 +180,7 @@ static DEVICE_START( namco_52xx )
 }
 
 
-void namco_52xx_write(const device_config *device, int data)
+WRITE8_DEVICE_HANDLER( namco_52xx_write )
 {
 	namco_52xx *chip = get_safe_token(device);
 	data &= 0x0f;
@@ -224,7 +224,7 @@ ADDRESS_MAP_END
 
 
 static MACHINE_DRIVER_START( namco_52xx )
-	MDRV_CPU_ADD("mcu", MB8842/*MB8852*/, DERIVED_CLOCK(1,6))		/* parent clock, internally divided by 6 */
+	MDRV_CPU_ADD("mcu", MB8843, DERIVED_CLOCK(1,6))		/* parent clock, internally divided by 6 */
 	MDRV_CPU_PROGRAM_MAP(namco_52xx_map_program)
 	MDRV_CPU_DATA_MAP(namco_52xx_map_data)
 	MDRV_CPU_IO_MAP(namco_52xx_map_io)
diff --git a/src/emu/sound/namco52.h b/src/emu/sound/namco52.h
index 399fbb361fc..c251c1ff266 100644
--- a/src/emu/sound/namco52.h
+++ b/src/emu/sound/namco52.h
@@ -28,7 +28,9 @@ struct _namco_52xx_interface
 	double	filt_gain;
 };
 
-void namco_52xx_write(const device_config *device, int data);
+
+WRITE8_DEVICE_HANDLER( namco_52xx_write );
+
 
 DEVICE_GET_INFO( namco_52xx );
 #define SOUND_NAMCO_52XX DEVICE_GET_INFO_NAME( namco_52xx )
diff --git a/src/mame/audio/namco54.c b/src/mame/audio/namco54.c
index 23564741c7d..86fb4869dd8 100644
--- a/src/mame/audio/namco54.c
+++ b/src/mame/audio/namco54.c
@@ -118,7 +118,7 @@ static TIMER_CALLBACK( namco_54xx_irq_clear )
 	cpu_set_input_line(state->cpu, 0, CLEAR_LINE);
 }
 
-void namco_54xx_write(const device_config *device, UINT8 data)
+WRITE8_DEVICE_HANDLER( namco_54xx_write )
 {
 	namco_54xx_state *state = get_safe_token(device);
 
@@ -165,7 +165,7 @@ MACHINE_DRIVER_END
 
 
 ROM_START( namco_54xx )
-	ROM_REGION( 0x400, "mcu", 0 )
+	ROM_REGION( 0x400, "mcu", ROMREGION_LOADBYNAME )
 	ROM_LOAD( "54xx.bin",     0x0000, 0x0400, CRC(ee7357e0) SHA1(01bdf984a49e8d0cc8761b2cc162fd6434d5afbe) )
 ROM_END
 
diff --git a/src/mame/audio/namco54.h b/src/mame/audio/namco54.h
index e39e1abd351..b8977800754 100644
--- a/src/mame/audio/namco54.h
+++ b/src/mame/audio/namco54.h
@@ -12,7 +12,6 @@ struct _namco_54xx_config
 };
 
 
-
 #define MDRV_NAMCO_54XX_ADD(_tag, _clock, _discrete, _firstnode) \
 	MDRV_DEVICE_ADD(_tag, NAMCO_54XX, _clock) \
 	MDRV_DEVICE_CONFIG_DATAPTR(namco_54xx_config, discrete, _discrete) \
@@ -22,12 +21,14 @@ struct _namco_54xx_config
 	MDRV_DEVICE_REMOVE(_tag)
 
 
-void namco_54xx_write(const device_config *device, UINT8 data);
+WRITE8_DEVICE_HANDLER( namco_54xx_write );
+
 
 /* device get info callback */
 #define NAMCO_54XX DEVICE_GET_INFO_NAME(namco_54xx)
 DEVICE_GET_INFO( namco_54xx );
 
+
 /* discrete nodes */
 #define NAMCO_54XX_0_DATA(base)		(NODE_RELATIVE(base, 0))
 #define NAMCO_54XX_1_DATA(base)		(NODE_RELATIVE(base, 1))
diff --git a/src/mame/drivers/galaga.c b/src/mame/drivers/galaga.c
index f6bb28bb316..57ac62db4d0 100644
--- a/src/mame/drivers/galaga.c
+++ b/src/mame/drivers/galaga.c
@@ -700,13 +700,14 @@ TODO:
 #include "machine/atari_vg.h"
 #include "machine/namcoio.h"
 #include "machine/namco50.h"
+#include "machine/namco51.h"
+#include "machine/namco53.h"
 #include "includes/galaga.h"
 #include "sound/namco.h"
 #include "sound/namco52.h"
 #include "machine/rescap.h"
 #include "sound/samples.h"
 #include "audio/namco54.h"
-#include "nam_cust.h"
 
 #define MASTER_CLOCK (XTAL_18_432MHz)
 
@@ -773,36 +774,47 @@ static WRITE8_HANDLER( bosco_latch_w )
 	}
 }
 
+static CUSTOM_INPUT( shifted_port_r ) { return input_port_read(field->port->machine, param) >> 4; }
 
-static READ8_HANDLER( in0_l )	{ return input_port_read(space->machine, "IN0"); }		// fire and start buttons
-static READ8_HANDLER( in0_h )	{ return input_port_read(space->machine, "IN0") >> 4; }	// coins
-static READ8_HANDLER( in1_l )	{ return input_port_read(space->machine, "IN1"); }		// P1 joystick
-static READ8_HANDLER( in1_h )	{ return input_port_read(space->machine, "IN1") >> 4; }	// P2 joystick
-static READ8_HANDLER( dipA_l )	{ return input_port_read(space->machine, "DSWA"); }		// dips A
-static READ8_HANDLER( dipA_h )	{ return input_port_read(space->machine, "DSWA") >> 4; }	// dips A
-static READ8_HANDLER( dipB_l )	{ return input_port_read(space->machine, "DSWB"); }		// dips B
-static READ8_HANDLER( dipB_h )	{ return input_port_read(space->machine, "DSWB") >> 4; }	// dips B
-static WRITE8_HANDLER( out_0 )
+static WRITE8_DEVICE_HANDLER( out_0 )
 {
 	set_led_status(1,data & 1);
 	set_led_status(0,data & 2);
 	coin_counter_w(1,~data & 4);
 	coin_counter_w(0,~data & 8);
 }
-static WRITE8_HANDLER( out_1 )
+
+static WRITE8_DEVICE_HANDLER( out_1 )
 {
 	coin_lockout_global_w(data & 1);
 }
 
-static const struct namcoio_interface intf0 =
+static const namco_51xx_interface namco_51xx_intf =
 {
-	{ in0_l, in0_h, in1_l, in1_h },	/* port read handlers */
-	{ out_0, out_1 }				/* port write handlers */
+	{	/* port read handlers */
+		DEVCB_INPUT_PORT("IN0L"),
+		DEVCB_INPUT_PORT("IN0H"),
+		DEVCB_INPUT_PORT("IN1L"),
+		DEVCB_INPUT_PORT("IN1H")
+	},
+	{	/* port write handlers */
+		DEVCB_HANDLER(out_0),
+		DEVCB_HANDLER(out_1)
+	}
 };
-static const struct namcoio_interface intf1 =
+
+static const namco_53xx_interface namco_53xx_intf =
 {
-	{ dipA_l, dipA_h, dipB_l, dipB_h },	/* port read handlers */
-	{ NULL, NULL }						/* port write handlers */
+	{	/* port read handlers */
+		DEVCB_INPUT_PORT("DSWA"),
+		DEVCB_INPUT_PORT("DSWA_HI"),
+		DEVCB_INPUT_PORT("DSWB"),
+		DEVCB_INPUT_PORT("DSWB_HI")
+	},
+	{	/* port write handlers */
+		DEVCB_NULL,
+		DEVCB_NULL
+	}
 };
 
 
@@ -843,7 +855,7 @@ static MACHINE_RESET( bosco )
 	bosco_latch_reset(machine);
 
 	namco_06xx_init(machine, 0, 0,
-		NAMCOIO_51XX, &intf0, NULL,
+		NAMCOIO_51XX, NULL,   "51xx",
 		NAMCOIO_NONE, NULL,   NULL,
 		NAMCOIO_50XX, NULL,   "50xx_1",
 		NAMCOIO_54XX, NULL,   "54xx");
@@ -863,7 +875,7 @@ static MACHINE_RESET( galaga )
 	bosco_latch_reset(machine);
 
 	namco_06xx_init(machine, 0, 0,
-		NAMCOIO_51XX, &intf0, NULL,
+		NAMCOIO_51XX, NULL,   "51xx",
 		NAMCOIO_NONE, NULL,   NULL,
 		NAMCOIO_NONE, NULL,   NULL,
 		NAMCOIO_54XX, NULL,   "54xx");
@@ -877,7 +889,7 @@ static MACHINE_RESET( xevious )
 	bosco_latch_reset(machine);
 
 	namco_06xx_init(machine, 0, 0,
-		NAMCOIO_51XX, &intf0, NULL,
+		NAMCOIO_51XX, NULL,   "51xx",
 		NAMCOIO_NONE, NULL,   NULL,
 		NAMCOIO_50XX, NULL,   "50xx",
 		NAMCOIO_54XX, NULL,   "54xx");
@@ -901,8 +913,8 @@ static MACHINE_RESET( digdug )
 	bosco_latch_reset(machine);
 
 	namco_06xx_init(machine, 0, 0,
-		NAMCOIO_51XX, &intf0, NULL,
-		NAMCOIO_53XX_DIGDUG, &intf1, NULL,
+		NAMCOIO_51XX, NULL, "51xx",
+		NAMCOIO_53XX, NULL, "53xx",
 		NAMCOIO_NONE, NULL, NULL,
 		NAMCOIO_NONE, NULL, NULL);
 
@@ -1015,25 +1027,29 @@ ADDRESS_MAP_END
 
 
 static INPUT_PORTS_START( bosco )
-	PORT_START("IN0")
+	PORT_START("IN0L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_COCKTAIL
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_START2 )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
-	PORT_SERVICE( 0x80, IP_ACTIVE_LOW )
 
-	PORT_START("IN1")
+	PORT_START("IN0H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SERVICE1 )
+	PORT_SERVICE( 0x08, IP_ACTIVE_LOW )
+
+	PORT_START("IN1L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY PORT_COCKTAIL
+
+	PORT_START("IN1H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY PORT_COCKTAIL
 
 	PORT_START("DSWA")
 	PORT_DIPNAME( 0x03, 0x03, DEF_STR( Difficulty ) )
@@ -1059,7 +1075,7 @@ static INPUT_PORTS_START( bosco )
 	PORT_DIPNAME( 0x80, 0x80, DEF_STR( Cabinet ) )
 	PORT_DIPSETTING(    0x80, DEF_STR( Upright ) )
 	PORT_DIPSETTING(    0x00, DEF_STR( Cocktail ) )
-
+	
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0x07, 0x07, DEF_STR( Coinage ) )
 	PORT_DIPSETTING(    0x01, DEF_STR( 4C_1C ) )
@@ -1118,25 +1134,29 @@ INPUT_PORTS_END
 
 
 static INPUT_PORTS_START( galaga )
-	PORT_START("IN0")
+	PORT_START("IN0L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_COCKTAIL
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_START2 )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
-	PORT_SERVICE( 0x80, IP_ACTIVE_LOW )
 
-	PORT_START("IN1")
+	PORT_START("IN0H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SERVICE1 )
+	PORT_SERVICE( 0x08, IP_ACTIVE_LOW )
+
+	PORT_START("IN1L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_2WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_2WAY
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_UNUSED )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_2WAY PORT_COCKTAIL
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_UNUSED )
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_2WAY PORT_COCKTAIL
+
+	PORT_START("IN1H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNUSED )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_2WAY PORT_COCKTAIL
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_UNUSED )
+	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_2WAY PORT_COCKTAIL
 
 	PORT_START("DSWA")
 	PORT_DIPNAME( 0x03, 0x03, DEF_STR( Difficulty ) )
@@ -1223,38 +1243,44 @@ INPUT_PORTS_END
 static INPUT_PORTS_START( gatsbee )
 	PORT_INCLUDE( galaga )
 
-	PORT_MODIFY("IN1")
+	PORT_MODIFY("IN1L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT )
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_UP )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_JOYSTICK_UP )    PORT_COCKTAIL
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_COCKTAIL
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN )  PORT_COCKTAIL
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT )  PORT_COCKTAIL
+
+	PORT_MODIFY("IN1L")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP )    PORT_COCKTAIL
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_COCKTAIL
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN )  PORT_COCKTAIL
+	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT )  PORT_COCKTAIL
 INPUT_PORTS_END
 
 
 static INPUT_PORTS_START( xevious )
-	PORT_START("IN0")
+	PORT_START("IN0L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_COCKTAIL
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_START2 )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
-	PORT_SERVICE( 0x80, IP_ACTIVE_LOW )
 
-	PORT_START("IN1")
+	PORT_START("IN0H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SERVICE1 )
+	PORT_SERVICE( 0x08, IP_ACTIVE_LOW )
+
+	PORT_START("IN1L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY PORT_COCKTAIL
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY PORT_COCKTAIL
+
+	PORT_START("IN1H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY PORT_COCKTAIL
+	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY PORT_COCKTAIL
 
 	PORT_START("DSWA")
 	PORT_DIPNAME( 0x03, 0x03, DEF_STR( Coin_A ) )
@@ -1388,25 +1414,29 @@ INPUT_PORTS_END
 
 
 static INPUT_PORTS_START( digdug )
-	PORT_START("IN0")
+	PORT_START("IN0L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_COCKTAIL
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_START2 )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
-	PORT_SERVICE( 0x80, IP_ACTIVE_LOW )
 
-	PORT_START("IN1")
+	PORT_START("IN0H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SERVICE1 )
+	PORT_SERVICE( 0x08, IP_ACTIVE_LOW )
+
+	PORT_START("IN1L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_4WAY
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_4WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_4WAY
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_4WAY
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_4WAY PORT_COCKTAIL
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_4WAY PORT_COCKTAIL
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_4WAY PORT_COCKTAIL
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_4WAY PORT_COCKTAIL
+
+	PORT_START("IN1H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_4WAY PORT_COCKTAIL
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_RIGHT ) PORT_4WAY PORT_COCKTAIL
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_4WAY PORT_COCKTAIL
+	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_4WAY PORT_COCKTAIL
 
 	PORT_START("DSWA")
 	PORT_DIPNAME( 0x07, 0x01, DEF_STR( Coin_B ) )
@@ -1441,6 +1471,9 @@ static INPUT_PORTS_START( digdug )
 	PORT_DIPSETTING(    0x80, "3" )
 	PORT_DIPSETTING(    0xc0, "5" )
 
+	PORT_START("DSWA_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWA")
+
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0xc0, 0x00, DEF_STR( Coin_A ) )
 	PORT_DIPSETTING(    0x40, DEF_STR( 2C_1C ) )
@@ -1464,6 +1497,9 @@ static INPUT_PORTS_START( digdug )
 	PORT_DIPSETTING(    0x02, DEF_STR( Medium ) )
 	PORT_DIPSETTING(    0x01, DEF_STR( Hard ) )
 	PORT_DIPSETTING(    0x03, DEF_STR( Hardest ) )
+
+	PORT_START("DSWB_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWB")
 INPUT_PORTS_END
 
 
@@ -1635,6 +1671,7 @@ static MACHINE_DRIVER_START( bosco )
 	
 	MDRV_NAMCO_50XX_ADD("50xx_1", MASTER_CLOCK/12)	/* 1.536 MHz */
 	MDRV_NAMCO_50XX_ADD("50xx_2", MASTER_CLOCK/12)	/* 1.536 MHz */
+	MDRV_NAMCO_51XX_ADD("51xx", MASTER_CLOCK/12, namco_51xx_intf)		/* 1.536 MHz */
 	MDRV_NAMCO_54XX_ADD("54xx", MASTER_CLOCK/12, "discrete", NODE_01)	/* 1.536 MHz */
 
 	MDRV_WATCHDOG_VBLANK_INIT(8)
@@ -1691,6 +1728,7 @@ static MACHINE_DRIVER_START( galaga )
 	MDRV_CPU_ADD("sub2", Z80, MASTER_CLOCK/6)	/* 3.072 MHz */
 	MDRV_CPU_PROGRAM_MAP(galaga_map)
 
+	MDRV_NAMCO_51XX_ADD("51xx", MASTER_CLOCK/12, namco_51xx_intf)		/* 1.536 MHz */
 	MDRV_NAMCO_54XX_ADD("54xx", MASTER_CLOCK/12, "discrete", NODE_01)	/* 1.536 MHz */
 
 	MDRV_WATCHDOG_VBLANK_INIT(8)
@@ -1758,6 +1796,7 @@ static MACHINE_DRIVER_START( xevious )
 	MDRV_CPU_PROGRAM_MAP(xevious_map)
 
 	MDRV_NAMCO_50XX_ADD("50xx", MASTER_CLOCK/12)	/* 1.536 MHz */
+	MDRV_NAMCO_51XX_ADD("51xx", MASTER_CLOCK/12, namco_51xx_intf)		/* 1.536 MHz */
 	MDRV_NAMCO_54XX_ADD("54xx", MASTER_CLOCK/12, "discrete", NODE_01)	/* 1.536 MHz */
 
 	MDRV_WATCHDOG_VBLANK_INIT(8)
@@ -1834,6 +1873,9 @@ static MACHINE_DRIVER_START( digdug )
 	MDRV_CPU_ADD("sub2", Z80, MASTER_CLOCK/6)	/* 3.072 MHz */
 	MDRV_CPU_PROGRAM_MAP(digdug_map)
 
+	MDRV_NAMCO_51XX_ADD("51xx", MASTER_CLOCK/12, namco_51xx_intf)		/* 1.536 MHz */
+	MDRV_NAMCO_53XX_ADD("53xx", MASTER_CLOCK/12, namco_53xx_intf)		/* 1.536 MHz */
+
 	MDRV_QUANTUM_TIME(HZ(6000))	/* 100 CPU slices per frame - an high value to ensure proper */
 							/* synchronization of the CPUs */
 	MDRV_MACHINE_START(galaga)
@@ -1891,10 +1933,6 @@ Namco/Midway, 1981
 
 */
 
-#define BOSCO_CUSTOMS \
-	ROM_REGION_NAMCO_51XX( "51xx" ) \
-
-
 ROM_START( bosco )
 	ROM_REGION( 0x10000, "maincpu", 0 )	/* 64k for code for the first CPU  */
 	ROM_LOAD( "bos3_1.bin",   0x0000, 0x1000, CRC(96021267) SHA1(bd49b0caabcccf9df45a272d767456a4fc8a7c07) )
@@ -1909,8 +1947,6 @@ ROM_START( bosco )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "2900.3e",      0x0000, 0x1000, CRC(d45a4911) SHA1(547236adca9174f5cc0ec05b9649618bb92ba630) )
 
-	BOSCO_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "5300.5d",      0x0000, 0x1000, CRC(a956d3c5) SHA1(c5a9d7b1f9b4acda8fb9762414e085cb5fb80c9e) )
 
@@ -1950,8 +1986,6 @@ ROM_START( boscoo )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "2900.3e",      0x0000, 0x1000, CRC(d45a4911) SHA1(547236adca9174f5cc0ec05b9649618bb92ba630) )
 
-	BOSCO_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "5300.5d",      0x0000, 0x1000, CRC(a956d3c5) SHA1(c5a9d7b1f9b4acda8fb9762414e085cb5fb80c9e) )
 
@@ -1991,8 +2025,6 @@ ROM_START( boscoo2 )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "2900.3e",      0x0000, 0x1000, CRC(d45a4911) SHA1(547236adca9174f5cc0ec05b9649618bb92ba630) )
 
-	BOSCO_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "5300.5d",      0x0000, 0x1000, CRC(a956d3c5) SHA1(c5a9d7b1f9b4acda8fb9762414e085cb5fb80c9e) )
 
@@ -2039,8 +2071,6 @@ ROM_START( boscomd )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "2900.3e",      0x0000, 0x1000, CRC(d45a4911) SHA1(547236adca9174f5cc0ec05b9649618bb92ba630) )
 
-	BOSCO_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "5300.5d",      0x0000, 0x1000, CRC(a956d3c5) SHA1(c5a9d7b1f9b4acda8fb9762414e085cb5fb80c9e) )
 
@@ -2083,8 +2113,6 @@ ROM_START( boscomdo )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "2900.3e",      0x0000, 0x1000, CRC(d45a4911) SHA1(547236adca9174f5cc0ec05b9649618bb92ba630) )
 
-	BOSCO_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "5300.5d",      0x0000, 0x1000, CRC(a956d3c5) SHA1(c5a9d7b1f9b4acda8fb9762414e085cb5fb80c9e) )
 
@@ -2280,10 +2308,6 @@ Notes:
 
 */
 
-#define GALAGA_CUSTOMS \
-	ROM_REGION_NAMCO_51XX( "51xx" ) \
-
-
 ROM_START( galaga )
 	ROM_REGION( 0x10000, "maincpu", 0 )     /* 64k for code for the first CPU  */
 	ROM_LOAD( "gg1-1b.3p",    0x0000, 0x1000, CRC(ab036c9f) SHA1(ca7f5da42d4e76fd89bb0b35198a23c01462fbfe) )
@@ -2297,8 +2321,6 @@ ROM_START( galaga )
 	ROM_REGION( 0x10000, "sub2", 0 )     /* 64k for the third CPU  */
 	ROM_LOAD( "gg1-7b.2c",    0x0000, 0x1000, CRC(d016686b) SHA1(44c1a04fba3c7c826ff484185cb881b4b22e6657) )
 
-	GALAGA_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "gg1-9.4l",     0x0000, 0x1000, CRC(58b2f47c) SHA1(62f1279a784ab2f8218c4137c7accda00e6a3490) )
 
@@ -2329,8 +2351,6 @@ ROM_START( galagao )
 	ROM_REGION( 0x10000, "sub2", 0 )     /* 64k for the third CPU  */
 	ROM_LOAD( "gg1-7",        0x0000, 0x1000, CRC(8995088d) SHA1(d6cb439de0718826d1a0363c9d77de8740b18ecf) )
 
-	GALAGA_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "gg1-9.4l",     0x0000, 0x1000, CRC(58b2f47c) SHA1(62f1279a784ab2f8218c4137c7accda00e6a3490) )
 
@@ -2361,8 +2381,6 @@ ROM_START( galagamw )
 	ROM_REGION( 0x10000, "sub2", 0 )     /* 64k for the third CPU  */
 	ROM_LOAD( "3700g.bin",    0x0000, 0x1000, CRC(b07f0aa4) SHA1(7528644a8480d0be2d0d37069515ed319e94778f) )
 
-	GALAGA_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "gg1-9.4l",     0x0000, 0x1000, CRC(58b2f47c) SHA1(62f1279a784ab2f8218c4137c7accda00e6a3490) )
 
@@ -2393,8 +2411,6 @@ ROM_START( galagamf )
 	ROM_REGION( 0x10000, "sub2", 0 )     /* 64k for the third CPU  */
 	ROM_LOAD( "3700g.bin",    0x0000, 0x1000, CRC(b07f0aa4) SHA1(7528644a8480d0be2d0d37069515ed319e94778f) )
 
-	GALAGA_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "gg1-9.4l",     0x0000, 0x1000, CRC(58b2f47c) SHA1(62f1279a784ab2f8218c4137c7accda00e6a3490) )
 
@@ -2425,8 +2441,6 @@ ROM_START( galagamk )
 	ROM_REGION( 0x10000, "sub2", 0 )     /* 64k for the third CPU  */
 	ROM_LOAD( "gg1-7b.2c",    0x0000, 0x1000, CRC(d016686b) SHA1(44c1a04fba3c7c826ff484185cb881b4b22e6657) )
 
-	GALAGA_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "gg1-9.4l",     0x0000, 0x1000, CRC(58b2f47c) SHA1(62f1279a784ab2f8218c4137c7accda00e6a3490) )
 
@@ -2514,9 +2528,6 @@ ROM_END
   Xevious & clones
 **********************************************************************************************/
 
-#define XEVIOUS_CUSTOMS \
-	ROM_REGION_NAMCO_51XX( "51xx" ) \
-
 /*
     Xevious - Namco Version
 
@@ -2537,8 +2548,6 @@ ROM_START( xevious )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2591,8 +2600,6 @@ ROM_START( xeviousa )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2641,8 +2648,6 @@ ROM_START( xeviousb )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2694,8 +2699,6 @@ ROM_START( xeviousc )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2753,9 +2756,6 @@ ROM_START( xevios )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	/* This is a bootleg, it probably shouldn't be loading these, see 'unknown roms' below */
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2858,8 +2858,6 @@ ROM_START( sxevious )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2908,8 +2906,6 @@ ROM_START( sxeviousj )
 	ROM_REGION( 0x10000, "sub2", 0 )
 	ROM_LOAD( "xvi_7.2c",     0x0000, 0x1000, CRC(dd35cf1c) SHA1(f8d1f8e019d8198308443c2e7e815d0d04b23d14) )
 
-	XEVIOUS_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "xvi_12.3b",    0x0000, 0x1000, CRC(088c8b26) SHA1(9c3b61dfca2f84673a78f7f66e363777a8f47a59) )	/* foreground characters */
 
@@ -2948,10 +2944,6 @@ ROM_END
   Dig Dug & clones
 **********************************************************************************************/
 
-#define DIGDUG_CUSTOMS \
-	ROM_REGION_NAMCO_51XX( "51xx" ) \
-	ROM_REGION_NAMCO_53XX( "53xx" ) \
-
 ROM_START( digdug )
 	ROM_REGION( 0x10000, "maincpu", 0 ) /* 64k for code for the first CPU  */
 	ROM_LOAD( "dd1a.1",       0x0000, 0x1000, CRC(a80ec984) SHA1(86689980410b9429cd7582c7a76342721c87d030) )
@@ -2966,8 +2958,6 @@ ROM_START( digdug )
 	ROM_REGION( 0x10000, "sub2", 0 ) /* 64k for the third CPU  */
 	ROM_LOAD( "136007.107",   0x0000, 0x1000, CRC(a41bce72) SHA1(2b9b74f56aa7939d9d47cf29497ae11f10d78598) )
 
-	DIGDUG_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "dd1.9",        0x0000, 0x0800, CRC(f14a6fe1) SHA1(0aa63300c2cb887196de590aceb98f3cf06fead4) )
 
@@ -3007,8 +2997,6 @@ ROM_START( digdugb )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "136007.107",   0x0000, 0x1000, CRC(a41bce72) SHA1(2b9b74f56aa7939d9d47cf29497ae11f10d78598) )
 
-	DIGDUG_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "dd1.9",        0x0000, 0x0800, CRC(f14a6fe1) SHA1(0aa63300c2cb887196de590aceb98f3cf06fead4) )
 
@@ -3067,8 +3055,6 @@ ROM_START( digdugat )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "136007.107",   0x0000, 0x1000, CRC(a41bce72) SHA1(2b9b74f56aa7939d9d47cf29497ae11f10d78598) )
 
-	DIGDUG_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "136007.108",   0x0000, 0x0800, CRC(3d24a3af) SHA1(857ae93e2a41258a129dcecbaed2df359540b735) )
 
@@ -3108,8 +3094,6 @@ ROM_START( digduga1 )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "136007.107",   0x0000, 0x1000, CRC(a41bce72) SHA1(2b9b74f56aa7939d9d47cf29497ae11f10d78598) )
 
-	DIGDUG_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "136007.108",   0x0000, 0x0800, CRC(3d24a3af) SHA1(857ae93e2a41258a129dcecbaed2df359540b735) )
 
@@ -3250,8 +3234,6 @@ ROM_START( digsid )
 	ROM_REGION( 0x10000, "sub2", 0 )	/* 64k for the third CPU  */
 	ROM_LOAD( "digdug6.6",   0x0000, 0x1000, CRC(a41bce72) SHA1(2b9b74f56aa7939d9d47cf29497ae11f10d78598) )
 
-	DIGDUG_CUSTOMS
-
 	ROM_REGION( 0x1000, "gfx1", ROMREGION_DISPOSE )
 	ROM_LOAD( "digdug8.8",        0x0000, 0x0800, CRC(f14a6fe1) SHA1(0aa63300c2cb887196de590aceb98f3cf06fead4) )
 
diff --git a/src/mame/drivers/polepos.c b/src/mame/drivers/polepos.c
index 99a65527cbe..f7c5519f2b6 100644
--- a/src/mame/drivers/polepos.c
+++ b/src/mame/drivers/polepos.c
@@ -212,15 +212,17 @@ Notes:
 
 #include "driver.h"
 #include "cpu/z80/z80.h"
+#include "cpu/z8000/z8000.h"
 #include "cpu/mb88xx/mb88xx.h"
 #include "deprecat.h"
 #include "machine/namcoio.h"
+#include "machine/namco51.h"
+#include "machine/namco53.h"
 #include "sound/namco.h"
 #include "sound/namco52.h"
 #include "sound/samples.h"
 #include "audio/namco54.h"
 #include "polepos.h"
-#include "nam_cust.h"
 
 #include "polepos.lh"
 
@@ -320,7 +322,7 @@ static WRITE8_HANDLER( polepos_latch_w )
 			break;
 
 		case 0x06:	/* SB0 */
-			auto_start_mask = 0xfb | (bit << 2);
+			auto_start_mask = !bit;
 			break;
 
 		case 0x07:	/* CHACL */
@@ -339,15 +341,10 @@ static WRITE16_HANDLER( polepos_z8002_nvi_enable_w )
 }
 
 
-static READ8_HANDLER( in0_l )	{ return input_port_read(space->machine, "IN0") & auto_start_mask; }	// fire and start buttons
-static READ8_HANDLER( in0_h )	{ return input_port_read(space->machine, "IN0") >> 4; }				// coins
-static READ8_HANDLER( dipA_l )	{ return input_port_read(space->machine, "DSWA"); }					// dips A
-static READ8_HANDLER( dipA_h )	{ return input_port_read(space->machine, "DSWA") >> 4; }				// dips A
-static READ8_HANDLER( dipB_l )	{ return input_port_read(space->machine, "DSWB"); }					// dips B
-static READ8_HANDLER( dipB_h )	{ return input_port_read(space->machine, "DSWB") >> 4; }				// dips B
-static READ8_HANDLER( in1_l )	{ return input_port_read(space->machine, "STEER"); }					// wheel
-static READ8_HANDLER( in1_h )	{ return input_port_read(space->machine, "STEER") >> 4; }				// wheel
-static WRITE8_HANDLER( out_0 )
+static CUSTOM_INPUT( shifted_port_r ) { return input_port_read(field->port->machine, param) >> 4; }
+static CUSTOM_INPUT( auto_start_r ) { return auto_start_mask; }
+
+static WRITE8_DEVICE_HANDLER( out_0 )
 {
 // no start lamps in pole position
 //  set_led_status(1,data & 1);
@@ -355,24 +352,41 @@ static WRITE8_HANDLER( out_0 )
 	coin_counter_w(1,~data & 4);
 	coin_counter_w(0,~data & 8);
 }
-static WRITE8_HANDLER( out_1 )
+
+static WRITE8_DEVICE_HANDLER( out_1 )
 {
 	coin_lockout_global_w(data & 1);
 }
 
-static const struct namcoio_interface intf0 =
+static const namco_51xx_interface namco_51xx_intf =
 {
-	{ in0_l, in0_h, dipB_l, dipB_h },	/* port read handlers */
-	{ out_0, out_1 }					/* port write handlers */
+	{	/* port read handlers */
+		DEVCB_INPUT_PORT("IN0L"),
+		DEVCB_INPUT_PORT("IN0H"),
+		DEVCB_INPUT_PORT("DSWB"),
+		DEVCB_INPUT_PORT("DSWB_HI")
+	},
+	{	/* port write handlers */
+		DEVCB_HANDLER(out_0),
+		DEVCB_HANDLER(out_1)
+	}
 };
-static const struct namcoio_interface intf1 =
+
+static const namco_53xx_interface namco_53xx_intf =
 {
-	{ in1_l, in1_h, dipA_l, dipA_h },	/* port read handlers */
-	{ NULL, NULL }						/* port write handlers */
+	{	/* port read handlers */
+		DEVCB_INPUT_PORT("STEER"),
+		DEVCB_INPUT_PORT("STEER_HI"),
+		DEVCB_INPUT_PORT("DSWA"),
+		DEVCB_INPUT_PORT("DSWA_HI")
+	},
+	{	/* port write handlers */
+		DEVCB_NULL,
+		DEVCB_NULL
+	}
 };
 
 
-#include "cpu/z8000/z8000.h"
 static MACHINE_RESET( polepos )
 {
 	const address_space *space = cputag_get_address_space(machine, "maincpu", ADDRESS_SPACE_PROGRAM);
@@ -383,8 +397,8 @@ static MACHINE_RESET( polepos )
 		polepos_latch_w(space, i, 0);
 
 	namco_06xx_init(machine, 0, 0,
-		NAMCOIO_51XX, &intf0, NULL,
-		NAMCOIO_53XX_POLEPOS, &intf1, NULL,
+		NAMCOIO_51XX, NULL, "51xx",
+		NAMCOIO_53XX, NULL, "53xx",
 		NAMCOIO_52XX, NULL, "namco52",
 		NAMCOIO_54XX, NULL, "54xx");
 
@@ -445,15 +459,17 @@ ADDRESS_MAP_END
  *********************************************************************/
 
 static INPUT_PORTS_START( polepos )
-	PORT_START("IN0")
+	PORT_START("IN0L")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_NAME("Gear Change") PORT_CODE(KEYCODE_SPACE) POLEPOS_TOGGLE /* Gear */
-	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL )	// start 1, program controlled
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL ) PORT_CUSTOM(auto_start_r, NULL)	// start 1, program controlled
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_UNUSED )
-	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
-	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
-	PORT_SERVICE( 0x80, IP_ACTIVE_LOW )
+
+	PORT_START("IN0H")
+	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
+	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_COIN2 )
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SERVICE1 )
+	PORT_SERVICE( 0x08, IP_ACTIVE_LOW )
 
 	PORT_START("DSWA")
 	PORT_DIPNAME( 0x07, 0x07, DEF_STR( Coin_A ) )
@@ -478,6 +494,9 @@ static INPUT_PORTS_START( polepos )
 	PORT_DIPNAME( 0x80, 0x80, "Nr. of Laps" )
 	PORT_DIPSETTING(	0x80, "3" )
 	PORT_DIPSETTING(	0x00, "4" )
+	
+	PORT_START("DSWA_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWA")
 
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0x07, 0x07, "Extended Rank" )
@@ -504,6 +523,9 @@ static INPUT_PORTS_START( polepos )
 	PORT_DIPNAME( 0x80, 0x00, DEF_STR( Demo_Sounds ) )
 	PORT_DIPSETTING(	0x80, DEF_STR( Off ))
 	PORT_DIPSETTING(	0x00, DEF_STR( On ) )
+	
+	PORT_START("DSWB_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWB")
 
 	PORT_START("BRAKE")
 	PORT_BIT( 0xff, 0x00, IPT_PEDAL2 ) PORT_MINMAX(0,0x90) PORT_SENSITIVITY(100) PORT_KEYDELTA(16)
@@ -513,6 +535,9 @@ static INPUT_PORTS_START( polepos )
 
 	PORT_START("STEER")
 	PORT_BIT( 0xff, 0x00, IPT_DIAL ) PORT_SENSITIVITY(30) PORT_KEYDELTA(4)
+	
+	PORT_START("STEER_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "STEER")
 INPUT_PORTS_END
 
 
@@ -520,7 +545,7 @@ static INPUT_PORTS_START( poleposa )
 	PORT_START("IN0")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_NAME("Gear Change") PORT_CODE(KEYCODE_SPACE) POLEPOS_TOGGLE /* Gear */
-	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL )	// start 1, program controlled
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL ) PORT_CUSTOM(auto_start_r, NULL) // start 1, program controlled
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
 	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
@@ -550,6 +575,9 @@ static INPUT_PORTS_START( poleposa )
 	PORT_DIPNAME( 0x01, 0x01, "Nr. of Laps" )
 	PORT_DIPSETTING(	0x01, "3" )
 	PORT_DIPSETTING(	0x00, "4" )
+	
+	PORT_START("DSWA_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWA")
 
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0xe0, 0xe0, "Practice Rank" )
@@ -577,6 +605,9 @@ static INPUT_PORTS_START( poleposa )
 	PORT_DIPSETTING(	0x01, DEF_STR( Off ))
 	PORT_DIPSETTING(	0x00, DEF_STR( On ) )
 
+	PORT_START("DSWB_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWB")
+
 	PORT_START("BRAKE")
 	PORT_BIT( 0xff, 0x00, IPT_PEDAL2 ) PORT_MINMAX(0,0x90) PORT_SENSITIVITY(100) PORT_KEYDELTA(16)
 
@@ -585,6 +616,9 @@ static INPUT_PORTS_START( poleposa )
 
 	PORT_START("STEER")
 	PORT_BIT( 0xff, 0x00, IPT_DIAL ) PORT_SENSITIVITY(30) PORT_KEYDELTA(4)
+	
+	PORT_START("STEER_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "STEER")
 INPUT_PORTS_END
 
 
@@ -593,7 +627,7 @@ static INPUT_PORTS_START( topracra )
 	PORT_START("IN0")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNKNOWN )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_UNKNOWN )
-	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL )	// start 1, program controlled
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL ) PORT_CUSTOM(auto_start_r, NULL)	// start 1, program controlled
 	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_UNKNOWN )
 	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_NAME("Gear Change") PORT_CODE(KEYCODE_SPACE) POLEPOS_TOGGLE /* Gear */
 	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_SERVICE1 )
@@ -622,6 +656,9 @@ static INPUT_PORTS_START( topracra )
 	PORT_DIPNAME( 0x80, 0x80, "Nr. of Laps" )
 	PORT_DIPSETTING(	0x80, "3" )
 	PORT_DIPSETTING(	0x00, "4" )
+	
+	PORT_START("DSWA_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWA")
 
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0x07, 0x07, "Extended Rank" )
@@ -649,6 +686,9 @@ static INPUT_PORTS_START( topracra )
 	PORT_DIPSETTING(	0x80, DEF_STR( Off ))
 	PORT_DIPSETTING(	0x00, DEF_STR( On ) )
 
+	PORT_START("DSWB_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWB")
+
 	PORT_START("BRAKE")
 	PORT_BIT( 0xff, 0x00, IPT_PEDAL2 ) PORT_MINMAX(0,0x90) PORT_SENSITIVITY(100) PORT_KEYDELTA(16)
 
@@ -657,6 +697,9 @@ static INPUT_PORTS_START( topracra )
 
 	PORT_START("STEER")
 	PORT_BIT( 0xff, 0x00, IPT_DIAL ) PORT_SENSITIVITY(30) PORT_KEYDELTA(4)
+	
+	PORT_START("STEER_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "STEER")
 INPUT_PORTS_END
 
 
@@ -664,7 +707,7 @@ static INPUT_PORTS_START( polepos2 )
 	PORT_START("IN0")
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON1 ) PORT_NAME("Gear Change") PORT_CODE(KEYCODE_SPACE) POLEPOS_TOGGLE /* Gear */
-	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL )	// start 1, program controlled
+	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_SPECIAL ) PORT_CUSTOM(auto_start_r, NULL)	// start 1, program controlled
 	PORT_BIT( 0x08, IP_ACTIVE_LOW, IPT_UNUSED )
 	PORT_BIT( 0x10, IP_ACTIVE_LOW, IPT_COIN1 )
 	PORT_BIT( 0x20, IP_ACTIVE_LOW, IPT_COIN2 )
@@ -695,6 +738,9 @@ static INPUT_PORTS_START( polepos2 )
 	PORT_DIPNAME( 0x01, 0x01, DEF_STR( Unknown ) )	/* docs say "freeze", but it doesn't seem to work */
 	PORT_DIPSETTING(	0x01, DEF_STR( Off ))
 	PORT_DIPSETTING(	0x00, DEF_STR( On ) )
+	
+	PORT_START("DSWA_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWA")
 
 	PORT_START("DSWB")
 	PORT_DIPNAME( 0x80, 0x80, DEF_STR( Game_Time ) )
@@ -719,6 +765,9 @@ static INPUT_PORTS_START( polepos2 )
 	PORT_DIPSETTING(	0x01, "Average" )
 	PORT_DIPSETTING(	0x00, DEF_STR( High ) )
 
+	PORT_START("DSWB_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "DSWB")
+
 	PORT_START("BRAKE")
 	PORT_BIT( 0xff, 0x00, IPT_PEDAL2 ) PORT_MINMAX(0,0x90) PORT_SENSITIVITY(100) PORT_KEYDELTA(16)
 
@@ -727,6 +776,9 @@ static INPUT_PORTS_START( polepos2 )
 
 	PORT_START("STEER")
 	PORT_BIT ( 0xff, 0x00, IPT_DIAL ) PORT_SENSITIVITY(30) PORT_KEYDELTA(4)
+	
+	PORT_START("STEER_HI")
+	PORT_BIT( 0x0f, 0x00, IPT_SPECIAL ) PORT_CUSTOM(shifted_port_r, "STEER")
 INPUT_PORTS_END
 
 
@@ -846,6 +898,8 @@ static MACHINE_DRIVER_START( polepos )
 	MDRV_CPU_PROGRAM_MAP(z8002_map)
 	MDRV_CPU_VBLANK_INT("screen", irq0_line_assert)
 
+	MDRV_NAMCO_51XX_ADD("51xx", 18432000/12, namco_51xx_intf)		/* 1.536 MHz */
+	MDRV_NAMCO_53XX_ADD("53xx", 18432000/12, namco_53xx_intf)		/* 1.536 MHz */
 	MDRV_NAMCO_54XX_ADD("54xx", 18432000/12, "discrete", NODE_01)	/* 1.536 MHz */
 
 	MDRV_WATCHDOG_VBLANK_INIT(16)	// 128V clocks the same as VBLANK
@@ -901,10 +955,6 @@ MACHINE_DRIVER_END
  * ROM definitions
  *********************************************************************/
 
-#define POLEPOS_CUSTOMS \
-	ROM_REGION_NAMCO_51XX( "51xx" ) \
-	ROM_REGION_NAMCO_53XX( "53xx" ) \
-
 /*
     Pole Position - Namco Version
 */
@@ -925,8 +975,6 @@ ROM_START( polepos )
 	ROM_LOAD16_BYTE( "pp1_5b.4m",     0x0001, 0x2000, CRC(5cdf5294) SHA1(dbdf327a541fd71aadafda9c925fa4cf7f7c4a24) )
 	ROM_LOAD16_BYTE( "pp1_6b.4l",     0x0000, 0x2000, CRC(81696272) SHA1(27041a7c24297a6f317537c44922b51d2b2278a6) )
 
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "pp1_28.1f",     0x0000, 0x1000, CRC(5b277daf) SHA1(0b1feeb2c0c63a5db5ba9b0115aa1b2388636a70) )
@@ -1011,8 +1059,6 @@ ROM_START( poleposa )
 	ROM_LOAD16_BYTE( "136014.203",   0x0001, 0x2000, CRC(eedea6e7) SHA1(e1459c5e3f824e589e624c3acb18a183fd160df6) )
 	ROM_LOAD16_BYTE( "136014.204",   0x0000, 0x2000, CRC(c52c98ed) SHA1(2e33c487deaf8afb941e07e511a9828d2d8f6b31) )
 
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "136014.132",   0x0000, 0x1000, CRC(a949aa85) SHA1(2d6414196b6071101001128418233e585279ffb9) )
@@ -1092,8 +1138,6 @@ ROM_START( polepos1 )
 	ROM_LOAD16_BYTE( "136014.103",   0x0001, 0x2000, CRC(af4fc019) SHA1(1bb6c0f3ffada2e1df72e1767581f8e8bb2b18f9) )
 	ROM_LOAD16_BYTE( "136014.104",   0x0000, 0x2000, CRC(ba0045f3) SHA1(aedb8d8c56407963aa4ffb66243288c8fd6d845a) )
 
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "136014.132",   0x0000, 0x1000, CRC(a949aa85) SHA1(2d6414196b6071101001128418233e585279ffb9) )
@@ -1270,9 +1314,6 @@ ROM_START( topracer )
 	ROM_LOAD16_BYTE( "tr5b.bin",     0x0001, 0x2000, CRC(4e5f7b9c) SHA1(d26b1f24dd9ef00388987890bc5b95d4db403815) )
 	ROM_LOAD16_BYTE( "tr6b.bin",     0x0000, 0x2000, CRC(9d038ada) SHA1(7a9496c3fb93fd1945393656f8510a0c6421a9ab) )
 
-	/* this is a bootleg, should we really be loading these? */
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "tr28.bin",     0x0000, 0x1000, CRC(b8217c96) SHA1(aba311bc3c4b118ba322a00e33e2d5cbe7bc6e4a) )
@@ -1347,9 +1388,6 @@ ROM_START( topracra )
 	ROM_LOAD16_BYTE( "tr5b.bin",     0x0001, 0x2000, CRC(4e5f7b9c) SHA1(d26b1f24dd9ef00388987890bc5b95d4db403815) )
 	ROM_LOAD16_BYTE( "pole-d",       0x0000, 0x2000, CRC(932bb5a7) SHA1(8045fe1f9b4b1973ec0d6705adf3ba3891bddaa1) )
 
-	/* this is a bootleg, should we really be loading these? */
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "tr28.bin",     0x0000, 0x1000, CRC(b8217c96) SHA1(aba311bc3c4b118ba322a00e33e2d5cbe7bc6e4a) )
@@ -1427,9 +1465,6 @@ ROM_START( topracrb )
 	ROM_LOAD16_BYTE( "tr5b.f7",     0x0001, 0x2000, CRC(4e5f7b9c) SHA1(d26b1f24dd9ef00388987890bc5b95d4db403815) )
 	ROM_LOAD16_BYTE( "tr6b.f5",     0x0000, 0x2000, CRC(b3641d0c) SHA1(38ce172b2e38895749cbd3cc1c0e2c0fe8be744a) )
 
-	/* this is a bootleg, should we really be loading these? */
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x01000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "tr28.j9",      0x0000, 0x1000, CRC(b8217c96) SHA1(aba311bc3c4b118ba322a00e33e2d5cbe7bc6e4a) )
@@ -1511,8 +1546,6 @@ ROM_START( polepos2 )
 	ROM_LOAD16_BYTE( "pp4_7.3m",      0x4001, 0x1000, CRC(ad1c8994) SHA1(2877de9641516767170c0109900955cc7d1ff402) )
 	ROM_LOAD16_BYTE( "pp4_8.3l",      0x4000, 0x1000, CRC(ef25a2ee) SHA1(45959355cad1a48f19ae14193374e03d4f9965c7) )
 
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x02000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "pp4_28.1f",     0x0000, 0x2000, CRC(280dde7d) SHA1(b7c7fb3a5076aa4d0e0cf3256ece9a6194315626) )
@@ -1605,8 +1638,6 @@ ROM_START( poleps2a )
 	ROM_LOAD16_BYTE( "136014.184",   0x4001, 0x2000, CRC(d893c4ed) SHA1(60d39abefbb0c8df68864a30b1f5fcbf4780c86c) )
 	ROM_LOAD16_BYTE( "136014.185",   0x4000, 0x2000, CRC(899de75e) SHA1(4a16535115e37a3d342b2cb53f610a87c0d0abe1) )
 
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x02000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "136014.172",   0x0000, 0x2000, CRC(fbe5e72f) SHA1(07965d6e98ac1332ac6192b5e9cc927dd9eb706f) )
@@ -1691,9 +1722,6 @@ ROM_START( poleps2b )
 	ROM_LOAD16_BYTE( "136014.184",   0x4001, 0x2000, CRC(d893c4ed) SHA1(60d39abefbb0c8df68864a30b1f5fcbf4780c86c) )
 	ROM_LOAD16_BYTE( "136014.185",   0x4000, 0x2000, CRC(899de75e) SHA1(4a16535115e37a3d342b2cb53f610a87c0d0abe1) )
 
-	/* this is a bootleg, should we really be loading these? */
-	POLEPOS_CUSTOMS
-
 	/* graphics data */
 	ROM_REGION( 0x02000, "gfx1", ROMREGION_DISPOSE ) 	/* 2bpp alpha layer */
 	ROM_LOAD( "136014.172",   0x0000, 0x2000, CRC(fbe5e72f) SHA1(07965d6e98ac1332ac6192b5e9cc927dd9eb706f) )
diff --git a/src/mame/includes/nam_cust.h b/src/mame/includes/nam_cust.h
deleted file mode 100644
index a8c5c484bca..00000000000
--- a/src/mame/includes/nam_cust.h
+++ /dev/null
@@ -1,19 +0,0 @@
-/* Namco Custom Chip ROM loading Macros */
-
-
-/* the 50XX is a player score controller, used for protection */
-
-/* the 51XX is an I/O controller */
-#define ROM_REGION_NAMCO_51XX( region ) \
-	ROM_REGION( 0x400, region, 0 ) /* 1k for the 51xx  */ \
-	ROM_LOAD( "51xx.bin",     0x0000, 0x0400, CRC(c2f57ef8) SHA1(50de79e0d6a76bda95ffb02fcce369a79e6abfec) ) \
-
-/* the 52XX is a sample player */
-
-/* the 53XX is an I/O controller */
-#define ROM_REGION_NAMCO_53XX( region ) \
-	ROM_REGION( 0x400, region, 0 ) /* 1k for the 53xx  */ \
-	ROM_LOAD( "53xx.bin",     0x0000, 0x0400, CRC(b326fecb) SHA1(758d8583d658e4f1df93184009d86c3eb8713899) ) \
-
-/* the 54XX is an explosion sound generator */
-
diff --git a/src/mame/machine/namco50.c b/src/mame/machine/namco50.c
index 29686b5ea61..f9c5e6ac560 100644
--- a/src/mame/machine/namco50.c
+++ b/src/mame/machine/namco50.c
@@ -222,7 +222,7 @@ static void namco_50xx_irq_set(const device_config *device)
 	timer_set(device->machine, ATTOTIME_IN_USEC(21), (void *)device, 0, namco_50xx_irq_clear);
 }
 
-void namco_50xx_write(const device_config *device, UINT8 data)
+WRITE8_DEVICE_HANDLER( namco_50xx_write )
 {
 	timer_call_after_resynch(device->machine, (void *)device, data, namco_50xx_latch_callback);
 
@@ -238,7 +238,7 @@ void namco_50xx_read_request(const device_config *device)
 }
 
 
-UINT8 namco_50xx_read(const device_config *device)
+READ8_DEVICE_HANDLER( namco_50xx_read )
 {
 	namco_50xx_state *state = get_safe_token(device);
 	UINT8 res = state->portO;
diff --git a/src/mame/machine/namco50.h b/src/mame/machine/namco50.h
index f021bbb05f2..c95d92165f7 100644
--- a/src/mame/machine/namco50.h
+++ b/src/mame/machine/namco50.h
@@ -9,9 +9,10 @@
 	MDRV_DEVICE_REMOVE(_tag)
 
 
-UINT8 namco_50xx_read(const device_config *device);
+READ8_DEVICE_HANDLER( namco_50xx_read );
 void namco_50xx_read_request(const device_config *device);
-void namco_50xx_write(const device_config *device, UINT8 data);
+WRITE8_DEVICE_HANDLER( namco_50xx_write );
+
 
 /* device get info callback */
 #define NAMCO_50XX DEVICE_GET_INFO_NAME(namco_50xx)
diff --git a/src/mame/machine/namco51.c b/src/mame/machine/namco51.c
new file mode 100644
index 00000000000..e5c2ace7408
--- /dev/null
+++ b/src/mame/machine/namco51.c
@@ -0,0 +1,452 @@
+/***************************************************************************
+
+Namco 51XX
+
+This custom chip is a Fujitsu MB8843 MCU programmed to act as an I/O device
+with built-in coin management.
+ protection
+device. It keeps track of the players scores, and checks if a high score has
+been obtained or bonus lives should be awarded. The main CPU has a range of
+commands to increment/decrement the score by various fixed amounts.
+
+The device is used to its full potential only by Bosconian; Xevious uses it
+too, but only to do a protection check on startup.
+
+CMD = command from main CPU
+ANS = answer to main CPU
+
+The chip reads/writes the I/O ports when the /IRQ is pulled down. Pin 21
+determines whether a read or write should happen (1=R, 0=W).
+
+        MB8843
+       +------+
+  EXTAL|1   42|Vcc
+   XTAL|2   41|K3
+ /RESET|3   40|K2
+   /IRQ|4   39|K1
+     SO|5   38|K0
+     SI|6   37|R15
+/SC /TO|7   36|R14
+    /TC|8   35|R13
+     P0|9   34|R12
+     P1|10  33|R11
+     P2|11  32|R10
+     P3|12  31|R9
+     O0|13  30|R8
+     O1|14  29|R7
+     O2|15  28|R6
+     O3|16  27|R5
+     O4|17  26|R4
+     O5|18  25|R3
+     O6|19  24|R2
+     O7|20  23|R1
+    GND|21  22|R0
+       +------+
+
+
+commands:
+00: nop
+01 + 4 arguments: set coinage (xevious, possibly because of a bug, is different)
+02: go in "credit" mode and enable start buttons
+03: disable joystick remapping
+04: enable joystick remapping
+05: go in "switch" mode
+06: nop
+07: nop
+
+***************************************************************************/
+
+#include "driver.h"
+#include "namco51.h"
+#include "cpu/mb88xx/mb88xx.h"
+
+
+#define VERBOSE 0
+#define LOG(x) do { if (VERBOSE) logerror x; } while (0)
+
+
+#define READ_PORT(st,num) 			devcb_call_read8(&(st)->in[num], 0)
+#define WRITE_PORT(st,num,data) 	devcb_call_write8(&(st)->out[num], 0, data)
+
+
+typedef struct _namco_51xx_state namco_51xx_state;
+struct _namco_51xx_state
+{
+	const device_config *	cpu;
+	devcb_resolved_read8 in[4];
+	devcb_resolved_write8 out[2];
+	INT32 lastcoins,lastbuttons;
+	INT32 credits;
+	INT32 coins[2];
+	INT32 coins_per_cred[2];
+	INT32 creds_per_coin[2];
+	INT32 in_count;
+	INT32 mode,coincred_mode,remap_joy;
+};
+
+INLINE namco_51xx_state *get_safe_token(const device_config *device)
+{
+	assert(device != NULL);
+	assert(device->token != NULL);
+	assert(device->type == NAMCO_51XX);
+
+	return (namco_51xx_state *)device->token;
+}
+
+
+
+WRITE8_DEVICE_HANDLER( namco_51xx_write )
+{
+	namco_51xx_state *state = get_safe_token(device);
+
+	data &= 0x07;
+
+	LOG(("%s: custom 51XX write %02x\n",cpuexec_describe_context(device->machine),data));
+
+	if (state->coincred_mode)
+	{
+		switch (state->coincred_mode--)
+		{
+			case 4: state->coins_per_cred[0] = data; break;
+			case 3: state->creds_per_coin[0] = data; break;
+			case 2: state->coins_per_cred[1] = data; break;
+			case 1: state->creds_per_coin[1] = data; break;
+		}
+	}
+	else
+	{
+		switch (data)
+		{
+			case 0:	// nop
+				break;
+
+			case 1:	// set coinage
+				state->coincred_mode = 4;
+				/* this is a good time to reset the credits counter */
+				state->credits = 0;
+
+				{
+					/* kludge for a possible bug in Xevious */
+					static const game_driver *namcoio_51XX_driver = NULL;
+					static int namcoio_51XX_kludge = 0;
+
+					/* Only compute namcoio_51XX_kludge when gamedrv changes */
+					if (namcoio_51XX_driver != device->machine->gamedrv)
+					{
+						namcoio_51XX_driver = device->machine->gamedrv;
+						if (strcmp(namcoio_51XX_driver->name, "xevious") == 0 ||
+							strcmp(namcoio_51XX_driver->parent, "xevious") == 0)
+							namcoio_51XX_kludge = 1;
+						else
+							namcoio_51XX_kludge = 0;
+					}
+
+					if (namcoio_51XX_kludge)
+					{
+						state->coincred_mode = 6;
+						state->remap_joy = 1;
+					}
+				}
+				break;
+
+			case 2:	// go in "credits" mode and enable start buttons
+				state->mode = 1;
+				state->in_count = 0;
+				break;
+
+			case 3:	// disable joystick remapping
+				state->remap_joy = 0;
+				break;
+
+			case 4:	// enable joystick remapping
+				state->remap_joy = 1;
+				break;
+
+			case 5:	// go in "switch" mode
+				state->mode = 0;
+				state->in_count = 0;
+				break;
+
+			default:
+				logerror("unknown 51XX command %02x\n",data);
+				break;
+		}
+	}
+}
+
+
+/* joystick input mapping
+
+  The joystick is parsed and a number corresponding to the direction is returned,
+  according to the following table:
+
+          0
+        7   1
+      6   8   2
+        5   3
+          4
+
+  The values for directions impossible to obtain on a joystick have not been
+  verified on Namco original hardware, but they are the same in all the bootlegs,
+  so we can assume they are right.
+*/
+static const int joy_map[16] =
+/*  LDRU, LDR, LDU,  LD, LRU, LR,  LU,    L, DRU,  DR,  DU,   D,  RU,   R,   U, center */
+{	 0xf, 0xe, 0xd, 0x5, 0xc, 0x9, 0x7, 0x6, 0xb, 0x3, 0xa, 0x4, 0x1, 0x2, 0x0, 0x8 };
+
+
+READ8_DEVICE_HANDLER( namco_51xx_read )
+{
+	namco_51xx_state *state = get_safe_token(device);
+
+	LOG(("%s: custom 51XX read\n",cpuexec_describe_context(device->machine)));
+
+	if (state->mode == 0)	/* switch mode */
+	{
+		switch ((state->in_count++) % 3)
+		{
+			default:
+			case 0: return READ_PORT(state,0) | (READ_PORT(state,1) << 4);
+			case 1: return READ_PORT(state,2) | (READ_PORT(state,3) << 4);
+			case 2: return 0;	// nothing?
+		}
+	}
+	else	/* credits mode */
+	{
+		switch ((state->in_count++) % 3)
+		{
+			default:
+			case 0:	// number of credits in BCD format
+				{
+					int in,toggle;
+
+					in = ~(READ_PORT(state,0) | (READ_PORT(state,1) << 4));
+					toggle = in ^ state->lastcoins;
+					state->lastcoins = in;
+
+					if (state->coins_per_cred[0] > 0)
+					{
+						if (state->credits >= 99)
+						{
+							WRITE_PORT(state,1,1);	// coin lockout
+						}
+						else
+						{
+							WRITE_PORT(state,1,0);	// coin lockout
+							/* check if the user inserted a coin */
+							if (toggle & in & 0x10)
+							{
+								state->coins[0]++;
+								WRITE_PORT(state,0,0x04);	// coin counter
+								WRITE_PORT(state,0,0x0c);
+								if (state->coins[0] >= state->coins_per_cred[0])
+								{
+									state->credits += state->creds_per_coin[0];
+									state->coins[0] -= state->coins_per_cred[0];
+								}
+							}
+							if (toggle & in & 0x20)
+							{
+								state->coins[1]++;
+								WRITE_PORT(state,0,0x08);	// coin counter
+								WRITE_PORT(state,0,0x0c);
+								if (state->coins[1] >= state->coins_per_cred[1])
+								{
+									state->credits += state->creds_per_coin[1];
+									state->coins[1] -= state->coins_per_cred[1];
+								}
+							}
+							if (toggle & in & 0x40)
+							{
+								state->credits++;
+							}
+						}
+					}
+					else state->credits = 100;	// free play
+
+					if (state->mode == 1)
+					{
+						int on = (video_screen_get_frame_number(device->machine->primary_screen) & 0x10) >> 4;
+
+						if (state->credits >= 2)
+							WRITE_PORT(state,0,0x0c | 3*on);	// lamps
+						else if (state->credits >= 1)
+							WRITE_PORT(state,0,0x0c | 2*on);	// lamps
+						else
+							WRITE_PORT(state,0,0x0c);	// lamps off
+
+						/* check for 1 player start button */
+						if (toggle & in & 0x04)
+						{
+							if (state->credits >= 1)
+							{
+								state->credits--;
+								state->mode = 2;
+								WRITE_PORT(state,0,0x0c);	// lamps off
+							}
+						}
+						/* check for 2 players start button */
+						else if (toggle & in & 0x08)
+						{
+							if (state->credits >= 2)
+							{
+								state->credits -= 2;
+								state->mode = 2;
+								WRITE_PORT(state, 0,0x0c);	// lamps off
+							}
+						}
+					}
+				}
+
+				if (~READ_PORT(state, 1) & 0x08)	/* check test mode switch */
+					return 0xbb;
+
+				return (state->credits / 10) * 16 + state->credits % 10;
+
+			case 1:
+				{
+					int joy = READ_PORT(state,2) & 0x0f;
+					int in,toggle;
+
+					in = ~READ_PORT(state,0);
+					toggle = in ^ state->lastbuttons;
+					state->lastbuttons = (state->lastbuttons & 2) | (in & 1);
+
+					/* remap joystick */
+					if (state->remap_joy) joy = joy_map[joy];
+
+					/* fire */
+					joy |= ((toggle & in & 0x01)^1) << 4;
+					joy |= ((in & 0x01)^1) << 5;
+
+					return joy;
+				}
+
+			case 2:
+				{
+					int joy = READ_PORT(state,3) & 0x0f;
+					int in,toggle;
+
+					in = ~READ_PORT(state,0);
+					toggle = in ^ state->lastbuttons;
+					state->lastbuttons = (state->lastbuttons & 1) | (in & 2);
+
+					/* remap joystick */
+					if (state->remap_joy) joy = joy_map[joy];
+
+					/* fire */
+					joy |= ((toggle & in & 0x02)^2) << 3;
+					joy |= ((in & 0x02)^2) << 4;
+
+					return joy;
+				}
+		}
+	}
+}
+
+
+
+
+
+/***************************************************************************
+    DEVICE INTERFACE
+***************************************************************************/
+
+ADDRESS_MAP_START( namco_51xx_map_program, ADDRESS_SPACE_PROGRAM, 8 )
+	AM_RANGE(0x000, 0x3ff) AM_ROM
+ADDRESS_MAP_END
+
+ADDRESS_MAP_START( namco_51xx_map_data, ADDRESS_SPACE_DATA, 8 )
+	AM_RANGE(0x00, 0x7f) AM_RAM
+ADDRESS_MAP_END
+
+ADDRESS_MAP_START( namco_51xx_map_io, ADDRESS_SPACE_IO, 8 )
+//	AM_RANGE(MB88_PORTK,  MB88_PORTK)  AM_READ(namco_51xx_K_r)
+//	AM_RANGE(MB88_PORTO,  MB88_PORTO)  AM_WRITE(namco_51xx_O_w)
+//	AM_RANGE(MB88_PORTR0, MB88_PORTR0) AM_READ(namco_51xx_R0_r)
+//	AM_RANGE(MB88_PORTR2, MB88_PORTR2) AM_READ(namco_51xx_R2_r)
+ADDRESS_MAP_END
+
+
+static MACHINE_DRIVER_START( namco_51xx )
+	MDRV_CPU_ADD("mcu", MB8843, DERIVED_CLOCK(1,6))		/* parent clock, internally divided by 6 */
+	MDRV_CPU_PROGRAM_MAP(namco_51xx_map_program)
+	MDRV_CPU_DATA_MAP(namco_51xx_map_data)
+	MDRV_CPU_IO_MAP(namco_51xx_map_io)
+	MDRV_CPU_FLAGS(CPU_DISABLE)
+MACHINE_DRIVER_END
+
+
+ROM_START( namco_51xx )
+	ROM_REGION( 0x400, "mcu", ROMREGION_LOADBYNAME )
+	ROM_LOAD( "51xx.bin",     0x0000, 0x0400, CRC(c2f57ef8) SHA1(50de79e0d6a76bda95ffb02fcce369a79e6abfec) )
+ROM_END
+
+
+/*-------------------------------------------------
+    device start callback
+-------------------------------------------------*/
+
+static DEVICE_START( namco_51xx )
+{
+	const namco_51xx_interface *config = (const namco_51xx_interface *)device->static_config;
+	namco_51xx_state *state = get_safe_token(device);
+	astring *tempstring = astring_alloc();
+	
+	assert(config != NULL);
+
+	/* find our CPU */
+	state->cpu = cputag_get_cpu(device->machine, device_build_tag(tempstring, device, "mcu"));
+	assert(state->cpu != NULL);
+	astring_free(tempstring);
+
+	/* resolve our read callbacks */
+	devcb_resolve_read8(&state->in[0], &config->in[0], device);
+	devcb_resolve_read8(&state->in[1], &config->in[1], device);
+	devcb_resolve_read8(&state->in[2], &config->in[2], device);
+	devcb_resolve_read8(&state->in[3], &config->in[3], device);
+
+	/* resolve our write callbacks */
+	devcb_resolve_write8(&state->out[0], &config->out[0], device);
+	devcb_resolve_write8(&state->out[1], &config->out[1], device);
+}
+
+
+/*-------------------------------------------------
+    device reset callback
+-------------------------------------------------*/
+
+static DEVICE_RESET( namco_51xx )
+{
+//	namco_51xx_state *state = get_safe_token(device);
+}
+
+
+/*-------------------------------------------------
+    device get info callback
+-------------------------------------------------*/
+
+DEVICE_GET_INFO( namco_51xx )
+{
+	switch (state)
+	{
+		/* --- the following bits of info are returned as 64-bit signed integers --- */
+		case DEVINFO_INT_TOKEN_BYTES:			info->i = sizeof(namco_51xx_state);				break;
+		case DEVINFO_INT_CLASS:					info->i = DEVICE_CLASS_PERIPHERAL;				break;
+
+		/* --- the following bits of info are returned as pointers --- */
+		case DEVINFO_PTR_ROM_REGION:			info->romregion = ROM_NAME(namco_51xx);			break;
+		case DEVINFO_PTR_MACHINE_CONFIG:		info->machine_config = MACHINE_DRIVER_NAME(namco_51xx); break;
+
+		/* --- the following bits of info are returned as pointers to data or functions --- */
+		case DEVINFO_FCT_START:					info->start = DEVICE_START_NAME(namco_51xx); 	break;
+		case DEVINFO_FCT_RESET:					info->reset = DEVICE_RESET_NAME(namco_51xx); 	break;
+
+		/* --- the following bits of info are returned as NULL-terminated strings --- */
+		case DEVINFO_STR_NAME:					strcpy(info->s, "Namco 51xx");					break;
+		case DEVINFO_STR_FAMILY:				strcpy(info->s, "Namco I/O");					break;
+		case DEVINFO_STR_VERSION:				strcpy(info->s, "1.0");							break;
+		case DEVINFO_STR_SOURCE_FILE:			strcpy(info->s, __FILE__);						break;
+		case DEVINFO_STR_CREDITS:				strcpy(info->s, "Copyright Nicola Salmoria and the MAME Team"); break;
+	}
+}
diff --git a/src/mame/machine/namco51.h b/src/mame/machine/namco51.h
new file mode 100644
index 00000000000..6512aab7feb
--- /dev/null
+++ b/src/mame/machine/namco51.h
@@ -0,0 +1,32 @@
+#ifndef NAMCO51_H
+#define NAMCO51_H
+
+#include "devcb.h"
+
+
+typedef struct _namco_51xx_interface namco_51xx_interface;
+struct _namco_51xx_interface
+{
+	devcb_read8 	in[4];		/* read handlers for ports A-D */
+	devcb_write8 	out[2];		/* write handlers for ports A-B */
+};
+
+
+#define MDRV_NAMCO_51XX_ADD(_tag, _clock, _interface) \
+	MDRV_DEVICE_ADD(_tag, NAMCO_51XX, _clock) \
+	MDRV_DEVICE_CONFIG(_interface)
+
+#define MDRV_NAMCO_51XX_REMOVE(_tag) \
+	MDRV_DEVICE_REMOVE(_tag)
+
+
+READ8_DEVICE_HANDLER( namco_51xx_read );
+WRITE8_DEVICE_HANDLER( namco_51xx_write );
+
+
+/* device get info callback */
+#define NAMCO_51XX DEVICE_GET_INFO_NAME(namco_51xx)
+DEVICE_GET_INFO( namco_51xx );
+
+
+#endif	/* NAMCO51_H */
diff --git a/src/mame/machine/namco53.c b/src/mame/machine/namco53.c
new file mode 100644
index 00000000000..b1bab77c8f4
--- /dev/null
+++ b/src/mame/machine/namco53.c
@@ -0,0 +1,201 @@
+/***************************************************************************
+
+Namco 53XX
+
+This custom chip is a Fujitsu MB8843 MCU programmed to act as an I/O device.
+
+The chip reads/writes the I/O ports when the /IRQ is pulled down. Pin 21
+determines whether a read or write should happen (1=R, 0=W).
+
+        MB8843
+       +------+
+  EXTAL|1   42|Vcc
+   XTAL|2   41|K3
+ /RESET|3   40|K2
+   /IRQ|4   39|K1
+     SO|5   38|K0
+     SI|6   37|R15
+/SC /TO|7   36|R14
+    /TC|8   35|R13
+     P0|9   34|R12
+     P1|10  33|R11
+     P2|11  32|R10
+     P3|12  31|R9
+     O0|13  30|R8
+     O1|14  29|R7
+     O2|15  28|R6
+     O3|16  27|R5
+     O4|17  26|R4
+     O5|18  25|R3
+     O6|19  24|R2
+     O7|20  23|R1
+    GND|21  22|R0
+       +------+
+
+
+commands:
+00: nop
+01 + 4 arguments: set coinage (xevious, possibly because of a bug, is different)
+02: go in "credit" mode and enable start buttons
+03: disable joystick remapping
+04: enable joystick remapping
+05: go in "switch" mode
+06: nop
+07: nop
+
+***************************************************************************/
+
+#include "driver.h"
+#include "namco53.h"
+#include "cpu/mb88xx/mb88xx.h"
+
+
+#define VERBOSE 0
+#define LOG(x) do { if (VERBOSE) logerror x; } while (0)
+
+
+#define READ_PORT(st,num) 			devcb_call_read8(&(st)->in[num], 0)
+#define WRITE_PORT(st,num,data) 	devcb_call_write8(&(st)->out[num], 0, data)
+
+
+typedef struct _namco_53xx_state namco_53xx_state;
+struct _namco_53xx_state
+{
+	const device_config *	cpu;
+	int in_count;
+	devcb_resolved_read8 in[4];
+	devcb_resolved_write8 out[2];
+};
+
+INLINE namco_53xx_state *get_safe_token(const device_config *device)
+{
+	assert(device != NULL);
+	assert(device->token != NULL);
+	assert(device->type == NAMCO_53XX);
+
+	return (namco_53xx_state *)device->token;
+}
+
+
+
+READ8_DEVICE_HANDLER( namco_53xx_read )
+{
+	namco_53xx_state *state = get_safe_token(device);
+
+	LOG(("%s: custom 53XX read\n",cpuexec_describe_context(device->machine)));
+
+// digdug: ((state->in_count++) % 2)
+	switch ((state->in_count++) % 8)
+	{
+		case 0: return READ_PORT(state,0) | (READ_PORT(state,1) << 4);	// steering
+// digdug: case 1:
+		case 4: return READ_PORT(state,2) | (READ_PORT(state,3) << 4);	// dip switches
+		default: return 0xff;	// polepos2 hangs if 0 is returned
+	}
+}
+
+
+
+
+/***************************************************************************
+    DEVICE INTERFACE
+***************************************************************************/
+
+ADDRESS_MAP_START( namco_53xx_map_program, ADDRESS_SPACE_PROGRAM, 8 )
+	AM_RANGE(0x000, 0x3ff) AM_ROM
+ADDRESS_MAP_END
+
+ADDRESS_MAP_START( namco_53xx_map_data, ADDRESS_SPACE_DATA, 8 )
+	AM_RANGE(0x00, 0x7f) AM_RAM
+ADDRESS_MAP_END
+
+ADDRESS_MAP_START( namco_53xx_map_io, ADDRESS_SPACE_IO, 8 )
+//	AM_RANGE(MB88_PORTK,  MB88_PORTK)  AM_READ(namco_53xx_K_r)
+//	AM_RANGE(MB88_PORTO,  MB88_PORTO)  AM_WRITE(namco_53xx_O_w)
+//	AM_RANGE(MB88_PORTR0, MB88_PORTR0) AM_READ(namco_53xx_R0_r)
+//	AM_RANGE(MB88_PORTR2, MB88_PORTR2) AM_READ(namco_53xx_R2_r)
+ADDRESS_MAP_END
+
+
+static MACHINE_DRIVER_START( namco_53xx )
+	MDRV_CPU_ADD("mcu", MB8843, DERIVED_CLOCK(1,6))		/* parent clock, internally divided by 6 */
+	MDRV_CPU_PROGRAM_MAP(namco_53xx_map_program)
+	MDRV_CPU_DATA_MAP(namco_53xx_map_data)
+	MDRV_CPU_IO_MAP(namco_53xx_map_io)
+	MDRV_CPU_FLAGS(CPU_DISABLE)
+MACHINE_DRIVER_END
+
+
+ROM_START( namco_53xx )
+	ROM_REGION( 0x400, "mcu", ROMREGION_LOADBYNAME )
+	ROM_LOAD( "53xx.bin",     0x0000, 0x0400, CRC(b326fecb) SHA1(758d8583d658e4f1df93184009d86c3eb8713899) )
+ROM_END
+
+
+/*-------------------------------------------------
+    device start callback
+-------------------------------------------------*/
+
+static DEVICE_START( namco_53xx )
+{
+	const namco_53xx_interface *config = (const namco_53xx_interface *)device->static_config;
+	namco_53xx_state *state = get_safe_token(device);
+	astring *tempstring = astring_alloc();
+	
+	assert(config != NULL);
+
+	/* find our CPU */
+	state->cpu = cputag_get_cpu(device->machine, device_build_tag(tempstring, device, "mcu"));
+	assert(state->cpu != NULL);
+	astring_free(tempstring);
+
+	/* resolve our read callbacks */
+	devcb_resolve_read8(&state->in[0], &config->in[0], device);
+	devcb_resolve_read8(&state->in[1], &config->in[1], device);
+	devcb_resolve_read8(&state->in[2], &config->in[2], device);
+	devcb_resolve_read8(&state->in[3], &config->in[3], device);
+
+	/* resolve our write callbacks */
+	devcb_resolve_write8(&state->out[0], &config->out[0], device);
+	devcb_resolve_write8(&state->out[1], &config->out[1], device);
+}
+
+
+/*-------------------------------------------------
+    device reset callback
+-------------------------------------------------*/
+
+static DEVICE_RESET( namco_53xx )
+{
+//	namco_53xx_state *state = get_safe_token(device);
+}
+
+
+/*-------------------------------------------------
+    device get info callback
+-------------------------------------------------*/
+
+DEVICE_GET_INFO( namco_53xx )
+{
+	switch (state)
+	{
+		/* --- the following bits of info are returned as 64-bit signed integers --- */
+		case DEVINFO_INT_TOKEN_BYTES:			info->i = sizeof(namco_53xx_state);				break;
+		case DEVINFO_INT_CLASS:					info->i = DEVICE_CLASS_PERIPHERAL;				break;
+
+		/* --- the following bits of info are returned as pointers --- */
+		case DEVINFO_PTR_ROM_REGION:			info->romregion = ROM_NAME(namco_53xx);			break;
+		case DEVINFO_PTR_MACHINE_CONFIG:		info->machine_config = MACHINE_DRIVER_NAME(namco_53xx); break;
+
+		/* --- the following bits of info are returned as pointers to data or functions --- */
+		case DEVINFO_FCT_START:					info->start = DEVICE_START_NAME(namco_53xx); 	break;
+		case DEVINFO_FCT_RESET:					info->reset = DEVICE_RESET_NAME(namco_53xx); 	break;
+
+		/* --- the following bits of info are returned as NULL-terminated strings --- */
+		case DEVINFO_STR_NAME:					strcpy(info->s, "Namco 53xx");					break;
+		case DEVINFO_STR_FAMILY:				strcpy(info->s, "Namco I/O");					break;
+		case DEVINFO_STR_VERSION:				strcpy(info->s, "1.0");							break;
+		case DEVINFO_STR_SOURCE_FILE:			strcpy(info->s, __FILE__);						break;
+		case DEVINFO_STR_CREDITS:				strcpy(info->s, "Copyright Nicola Salmoria and the MAME Team"); break;
+	}
+}
diff --git a/src/mame/machine/namco53.h b/src/mame/machine/namco53.h
new file mode 100644
index 00000000000..40f53419f71
--- /dev/null
+++ b/src/mame/machine/namco53.h
@@ -0,0 +1,31 @@
+#ifndef NAMCO53_H
+#define NAMCO53_H
+
+#include "devcb.h"
+
+
+typedef struct _namco_53xx_interface namco_53xx_interface;
+struct _namco_53xx_interface
+{
+	devcb_read8 	in[4];		/* read handlers for ports A-D */
+	devcb_write8 	out[2];		/* write handlers for ports A-B */
+};
+
+
+#define MDRV_NAMCO_53XX_ADD(_tag, _clock, _interface) \
+	MDRV_DEVICE_ADD(_tag, NAMCO_53XX, _clock) \
+	MDRV_DEVICE_CONFIG(_interface)
+
+#define MDRV_NAMCO_53XX_REMOVE(_tag) \
+	MDRV_DEVICE_REMOVE(_tag)
+
+
+READ8_DEVICE_HANDLER( namco_53xx_read );
+
+
+/* device get info callback */
+#define NAMCO_53XX DEVICE_GET_INFO_NAME(namco_53xx)
+DEVICE_GET_INFO( namco_53xx );
+
+
+#endif	/* NAMCO53_H */
diff --git a/src/mame/machine/namcoio.c b/src/mame/machine/namcoio.c
index d461b45db04..ab2e89a1506 100644
--- a/src/mame/machine/namcoio.c
+++ b/src/mame/machine/namcoio.c
@@ -135,6 +135,8 @@ TODO:
 #include "driver.h"
 #include "machine/namcoio.h"
 #include "machine/namco50.h"
+#include "machine/namco51.h"
+#include "machine/namco53.h"
 #include "sound/namco52.h"
 #include "audio/namco54.h"
 
@@ -170,268 +172,6 @@ static WRITE8_HANDLER( nop_w ) { }
 
 
 
-/*
-51XX
-
-commands:
-00: nop
-01 + 4 arguments: set coinage (xevious, possibly because of a bug, is different)
-02: go in "credit" mode and enable start buttons
-03: disable joystick remapping
-04: enable joystick remapping
-05: go in "switch" mode
-06: nop
-07: nop
-*/
-
-static void namcoio_51XX_write(running_machine *machine,int chip,int data)
-{
-	data &= 0x07;
-
-	LOG(("%s: custom 51XX write %02x\n",cpuexec_describe_context(machine),data));
-
-	if (io[chip].coincred_mode)
-	{
-		switch (io[chip].coincred_mode--)
-		{
-			case 4: io[chip].coins_per_cred[0] = data; break;
-			case 3: io[chip].creds_per_coin[0] = data; break;
-			case 2: io[chip].coins_per_cred[1] = data; break;
-			case 1: io[chip].creds_per_coin[1] = data; break;
-		}
-	}
-	else
-	{
-		switch (data)
-		{
-			case 0:	// nop
-				break;
-
-			case 1:	// set coinage
-				io[chip].coincred_mode = 4;
-				/* this is a good time to reset the credits counter */
-				io[chip].credits = 0;
-
-				{
-					/* kludge for a possible bug in Xevious */
-					static const game_driver *namcoio_51XX_driver = NULL;
-					static int namcoio_51XX_kludge = 0;
-
-					/* Only compute namcoio_51XX_kludge when gamedrv changes */
-					if (namcoio_51XX_driver != machine->gamedrv)
-					{
-						namcoio_51XX_driver = machine->gamedrv;
-						if (strcmp(namcoio_51XX_driver->name, "xevious") == 0 ||
-							strcmp(namcoio_51XX_driver->parent, "xevious") == 0)
-							namcoio_51XX_kludge = 1;
-						else
-							namcoio_51XX_kludge = 0;
-					}
-
-					if (namcoio_51XX_kludge)
-					{
-						io[chip].coincred_mode = 6;
-						io[chip].remap_joy = 1;
-					}
-				}
-				break;
-
-			case 2:	// go in "credits" mode and enable start buttons
-				io[chip].mode = 1;
-				io[chip].in_count = 0;
-				break;
-
-			case 3:	// disable joystick remapping
-				io[chip].remap_joy = 0;
-				break;
-
-			case 4:	// enable joystick remapping
-				io[chip].remap_joy = 1;
-				break;
-
-			case 5:	// go in "switch" mode
-				io[chip].mode = 0;
-				io[chip].in_count = 0;
-				break;
-
-			default:
-				logerror("unknown 51XX command %02x\n",data);
-				break;
-		}
-	}
-}
-
-
-/* joystick input mapping
-
-  The joystick is parsed and a number corresponding to the direction is returned,
-  according to the following table:
-
-          0
-        7   1
-      6   8   2
-        5   3
-          4
-
-  The values for directions impossible to obtain on a joystick have not been
-  verified on Namco original hardware, but they are the same in all the bootlegs,
-  so we can assume they are right.
-*/
-static const int joy_map[16] =
-/*  LDRU, LDR, LDU,  LD, LRU, LR,  LU,    L, DRU,  DR,  DU,   D,  RU,   R,   U, center */
-{	 0xf, 0xe, 0xd, 0x5, 0xc, 0x9, 0x7, 0x6, 0xb, 0x3, 0xa, 0x4, 0x1, 0x2, 0x0, 0x8 };
-
-
-static UINT8 namcoio_51XX_read(running_machine *machine, int chip)
-{
-	const address_space *space = cpu_get_address_space(machine->cpu[0], ADDRESS_SPACE_PROGRAM);
-
-	LOG(("%s: custom 51XX read\n",cpuexec_describe_context(machine)));
-
-	if (io[chip].mode == 0)	/* switch mode */
-	{
-		switch ((io[chip].in_count++) % 3)
-		{
-			default:
-			case 0: return READ_PORT(space,0) | (READ_PORT(space,1) << 4);
-			case 1: return READ_PORT(space,2) | (READ_PORT(space,3) << 4);
-			case 2: return 0;	// nothing?
-		}
-	}
-	else	/* credits mode */
-	{
-		switch ((io[chip].in_count++) % 3)
-		{
-			default:
-			case 0:	// number of credits in BCD format
-				{
-					int in,toggle;
-
-					in = ~(READ_PORT(space,0) | (READ_PORT(space,1) << 4));
-					toggle = in ^ io[chip].lastcoins;
-					io[chip].lastcoins = in;
-
-					if (io[chip].coins_per_cred[0] > 0)
-					{
-						if (io[chip].credits >= 99)
-						{
-							WRITE_PORT(space,1,1);	// coin lockout
-						}
-						else
-						{
-							WRITE_PORT(space,1,0);	// coin lockout
-							/* check if the user inserted a coin */
-							if (toggle & in & 0x10)
-							{
-								io[chip].coins[0]++;
-								WRITE_PORT(space,0,0x04);	// coin counter
-								WRITE_PORT(space,0,0x0c);
-								if (io[chip].coins[0] >= io[chip].coins_per_cred[0])
-								{
-									io[chip].credits += io[chip].creds_per_coin[0];
-									io[chip].coins[0] -= io[chip].coins_per_cred[0];
-								}
-							}
-							if (toggle & in & 0x20)
-							{
-								io[chip].coins[1]++;
-								WRITE_PORT(space,0,0x08);	// coin counter
-								WRITE_PORT(space,0,0x0c);
-								if (io[chip].coins[1] >= io[chip].coins_per_cred[1])
-								{
-									io[chip].credits += io[chip].creds_per_coin[1];
-									io[chip].coins[1] -= io[chip].coins_per_cred[1];
-								}
-							}
-							if (toggle & in & 0x40)
-							{
-								io[chip].credits++;
-							}
-						}
-					}
-					else io[chip].credits = 100;	// free play
-
-					if (io[chip].mode == 1)
-					{
-						int on = (video_screen_get_frame_number(machine->primary_screen) & 0x10) >> 4;
-
-						if (io[chip].credits >= 2)
-							WRITE_PORT(space,0,0x0c | 3*on);	// lamps
-						else if (io[chip].credits >= 1)
-							WRITE_PORT(space,0,0x0c | 2*on);	// lamps
-						else
-							WRITE_PORT(space,0,0x0c);	// lamps off
-
-						/* check for 1 player start button */
-						if (toggle & in & 0x04)
-						{
-							if (io[chip].credits >= 1)
-							{
-								io[chip].credits--;
-								io[chip].mode = 2;
-								WRITE_PORT(space,0,0x0c);	// lamps off
-							}
-						}
-						/* check for 2 players start button */
-						else if (toggle & in & 0x08)
-						{
-							if (io[chip].credits >= 2)
-							{
-								io[chip].credits -= 2;
-								io[chip].mode = 2;
-								WRITE_PORT(space, 0,0x0c);	// lamps off
-							}
-						}
-					}
-				}
-
-				if (~input_port_read(machine, "IN0") & 0x80)	/* check test mode switch */
-					return 0xbb;
-
-				return (io[chip].credits / 10) * 16 + io[chip].credits % 10;
-
-			case 1:
-				{
-					int joy = READ_PORT(space,2) & 0x0f;
-					int in,toggle;
-
-					in = ~READ_PORT(space,0);
-					toggle = in ^ io[chip].lastbuttons;
-					io[chip].lastbuttons = (io[chip].lastbuttons & 2) | (in & 1);
-
-					/* remap joystick */
-					if (io[chip].remap_joy) joy = joy_map[joy];
-
-					/* fire */
-					joy |= ((toggle & in & 0x01)^1) << 4;
-					joy |= ((in & 0x01)^1) << 5;
-
-					return joy;
-				}
-
-			case 2:
-				{
-					int joy = READ_PORT(space,3) & 0x0f;
-					int in,toggle;
-
-					in = ~READ_PORT(space,0);
-					toggle = in ^ io[chip].lastbuttons;
-					io[chip].lastbuttons = (io[chip].lastbuttons & 1) | (in & 2);
-
-					/* remap joystick */
-					if (io[chip].remap_joy) joy = joy_map[joy];
-
-					/* fire */
-					joy |= ((toggle & in & 0x02)^2) << 3;
-					joy |= ((in & 0x02)^2) << 4;
-
-					return joy;
-				}
-		}
-	}
-}
-
-
 /***************************************************************************/
 
 
@@ -876,46 +616,15 @@ void namco_06xx_init(running_machine *machine, int chipnum, int cpu,
 
 
 
-static UINT8 namcoio_53XX_digdug_read(running_machine *machine, int chip)
-{
-	const address_space *space = cpu_get_address_space(machine->cpu[0], ADDRESS_SPACE_PROGRAM);
-
-	LOG(("%s: custom 53XX read\n",cpuexec_describe_context(machine)));
-
-	switch ((io[chip].in_count++) % 2)
-	{
-		default:
-		case 0: return READ_PORT(space,0) | (READ_PORT(space,1) << 4);
-		case 1: return READ_PORT(space,2) | (READ_PORT(space,3) << 4);
-	}
-}
-
-
-static UINT8 namcoio_53XX_polepos_read(running_machine *machine,int chip)
-{
-	const address_space *space = cpu_get_address_space(machine->cpu[0], ADDRESS_SPACE_PROGRAM);
-
-	LOG(("%s: custom 53XX read\n",cpuexec_describe_context(machine)));
-
-	switch ((io[chip].in_count++) % 8)
-	{
-		case 0: return READ_PORT(space,0) | (READ_PORT(space,1) << 4);	// steering
-		case 4: return READ_PORT(space,2) | (READ_PORT(space,3) << 4);	// dip switches
-		default: return 0xff;	// polepos2 hangs if 0 is returned
-	}
-}
-
-
 static UINT8 namco_06xx_data_read(running_machine *machine, int chipnum)
 {
 	LOG(("forwarding read to chip %d\n",chipnum%3));
 
 	switch (io[chipnum].type)
 	{
-		case NAMCOIO_50XX:   return namco_50xx_read(io[chipnum].device);
-		case NAMCOIO_51XX: return namcoio_51XX_read(machine, chipnum);
-		case NAMCOIO_53XX_DIGDUG:  return namcoio_53XX_digdug_read(machine, chipnum);
-		case NAMCOIO_53XX_POLEPOS: return namcoio_53XX_polepos_read(machine, chipnum);
+		case NAMCOIO_50XX:	return namco_50xx_read(io[chipnum].device, 0);
+		case NAMCOIO_51XX:	return namco_51xx_read(io[chipnum].device, 0);
+		case NAMCOIO_53XX:	return namco_53xx_read(io[chipnum].device, 0);
 		default:
 			logerror("%s: custom IO type %d unsupported read\n",cpuexec_describe_context(machine),io[chipnum].type);
 			return 0xff;
@@ -929,10 +638,10 @@ static void namco_06xx_data_write(running_machine *machine,int chipnum,UINT8 dat
 
 	switch (io[chipnum].type)
 	{
-		case NAMCOIO_50XX:   namco_50xx_write(io[chipnum].device, data); break;
-		case NAMCOIO_51XX:   namcoio_51XX_write(machine,chipnum,data); break;
-		case NAMCOIO_52XX:   namco_52xx_write(io[chipnum].device, data); break;
-		case NAMCOIO_54XX:   namco_54xx_write(io[chipnum].device, data); break;
+		case NAMCOIO_50XX:   namco_50xx_write(io[chipnum].device, 0, data); break;
+		case NAMCOIO_51XX:   namco_51xx_write(io[chipnum].device, 0, data); break;
+		case NAMCOIO_52XX:   namco_52xx_write(io[chipnum].device, 0, data); break;
+		case NAMCOIO_54XX:   namco_54xx_write(io[chipnum].device, 0, data); break;
 		default:
 			logerror("%s: custom IO type %d unsupported write\n",cpuexec_describe_context(machine),io[chipnum].type);
 			break;
diff --git a/src/mame/machine/namcoio.h b/src/mame/machine/namcoio.h
index e7c0a25fd77..6097fe0c45a 100644
--- a/src/mame/machine/namcoio.h
+++ b/src/mame/machine/namcoio.h
@@ -9,8 +9,7 @@ enum
 	NAMCOIO_50XX,
 	NAMCOIO_51XX,
 	NAMCOIO_52XX,
-	NAMCOIO_53XX_DIGDUG,
-	NAMCOIO_53XX_POLEPOS,
+	NAMCOIO_53XX,
 	NAMCOIO_54XX,
 	NAMCOIO_56XX,
 	NAMCOIO_58XX,
diff --git a/src/mame/mame.mak b/src/mame/mame.mak
index 9e82d5a8543..ed30264ee76 100644
--- a/src/mame/mame.mak
+++ b/src/mame/mame.mak
@@ -940,6 +940,8 @@ $(MAMEOBJ)/namco.a: \
 	$(MACHINE)/namcoio.o \
 	$(AUDIO)/geebee.o \
 	$(MACHINE)/namco50.o \
+	$(MACHINE)/namco51.o \
+	$(MACHINE)/namco53.o \
 	$(AUDIO)/namco54.o \
 	$(AUDIO)/namcoc7x.o \
 	$(VIDEO)/bosco.o \