diff --git a/src/mame/drivers/segas16b.c b/src/mame/drivers/segas16b.c
index c46d8e0b3bb..343db21e859 100644
--- a/src/mame/drivers/segas16b.c
+++ b/src/mame/drivers/segas16b.c
@@ -3059,8 +3059,9 @@ static INPUT_PORTS_START( wrestwar )
 INPUT_PORTS_END
 
 
+/* we use common sys16b tags to simplify port reads */
 static INPUT_PORTS_START( atomicp )
-	PORT_START_TAG("IN0")
+	PORT_START_TAG("SERVICE")	/* P1 */
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY
@@ -3070,7 +3071,7 @@ static INPUT_PORTS_START( atomicp )
 	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_COIN2 )
 
-	PORT_START_TAG("IN1")
+	PORT_START_TAG("P1")	/* P2 */
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY PORT_PLAYER(2)
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY PORT_PLAYER(2)
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY PORT_PLAYER(2)
@@ -3080,7 +3081,7 @@ static INPUT_PORTS_START( atomicp )
 	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_START2 )
 	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_COIN1 )
 
-	PORT_START_TAG("DSW1")
+	PORT_START_TAG("UNUSED")	/* DSW1 */
 	PORT_DIPNAME( 0x07, 0x07, DEF_STR( Coin_B ) ) PORT_DIPLOCATION("SW1:1,2,3")
 	PORT_DIPSETTING(    0x00, DEF_STR( 4C_1C ) )
 	PORT_DIPSETTING(    0x04, DEF_STR( 3C_1C ) )
@@ -3105,7 +3106,7 @@ static INPUT_PORTS_START( atomicp )
 	PORT_DIPSETTING(    0x40, "3" )
 	PORT_DIPSETTING(    0x00, "5" )
 
-	PORT_START_TAG("DSW2")
+	PORT_START_TAG("P2")	/* DSW2 */
 	PORT_DIPNAME( 0x03, 0x03, DEF_STR( Difficulty ) ) PORT_DIPLOCATION("SW2:1,2")
 	PORT_DIPSETTING(    0x01, DEF_STR( Easy ) )
 	PORT_DIPSETTING(    0x03, DEF_STR( Normal ) )
@@ -3128,14 +3129,15 @@ static INPUT_PORTS_START( atomicp )
 	PORT_DIPSETTING(    0x00, "Atomic Point" )
 	PORT_SERVICE_DIPLOC( 0x80, IP_ACTIVE_HIGH, "SW2:8" )
 
-	PORT_START_TAG("DUMMY1")
+	PORT_START_TAG("DSW2")	/* DUMMY */
 
-	PORT_START_TAG("DUMMY2")
+	PORT_START_TAG("DSW1")	/* DUMMY */
 INPUT_PORTS_END
 
 
+/* we use common sys16b tags to simplify port reads */
 static INPUT_PORTS_START( snapper )
-	PORT_START_TAG("IN0")
+	PORT_START_TAG("SERVICE")	/* P1 */
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_JOYSTICK_UP ) PORT_8WAY
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_JOYSTICK_DOWN ) PORT_8WAY
 	PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_JOYSTICK_LEFT ) PORT_8WAY
@@ -3145,12 +3147,12 @@ static INPUT_PORTS_START( snapper )
 	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_BUTTON3 )
 	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_UNUSED )
 
-	PORT_START_TAG("IN1")
+	PORT_START_TAG("P1")	/* SYSTEM */
 	PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_COIN1 )
 	PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_START1 )
 	PORT_BIT( 0xfc, IP_ACTIVE_LOW, IPT_UNUSED )
 
-	PORT_START_TAG("DSW0")
+	PORT_START_TAG("UNUSED")	/* DSW0 */
 	PORT_DIPNAME( 0x07, 0x07, DEF_STR( Coin_B ) ) PORT_DIPLOCATION("SW0:1,2,3")
 	PORT_DIPSETTING(    0x00, DEF_STR( 4C_1C ) )
 	PORT_DIPSETTING(    0x04, DEF_STR( 3C_1C ) )
@@ -3175,7 +3177,7 @@ static INPUT_PORTS_START( snapper )
 	PORT_DIPSETTING(    0x40, "3" )
 	PORT_DIPSETTING(    0x00, "5" )
 
-	PORT_START_TAG("DSW1")
+	PORT_START_TAG("P2")	/* DSW1 */
 	PORT_DIPNAME( 0x01, 0x01, DEF_STR( Unknown ) ) PORT_DIPLOCATION("SW1:1")
 	PORT_DIPSETTING(    0x01, DEF_STR( Off ) )
 	PORT_DIPSETTING(    0x00, DEF_STR( On ) )
@@ -3199,9 +3201,9 @@ static INPUT_PORTS_START( snapper )
 	PORT_DIPSETTING(    0x00, DEF_STR( On ) )
 	PORT_SERVICE_DIPLOC( 0x80, IP_ACTIVE_LOW, "SW1:8" )
 
-	PORT_START_TAG("DUMMY1")
+	PORT_START_TAG("DSW2")	/* DUMMY */
 
-	PORT_START_TAG("DUMMY2")
+	PORT_START_TAG("DSW1")	/* DUMMY */
 INPUT_PORTS_END