diff --git a/src/mame/drivers/cischeat.c b/src/mame/drivers/cischeat.c
index db230cd02f7..8aaa90e6401 100644
--- a/src/mame/drivers/cischeat.c
+++ b/src/mame/drivers/cischeat.c
@@ -227,7 +227,7 @@ static WRITE16_HANDLER( bigrun_paletteram16_w )
 static ADDRESS_MAP_START( bigrun_map, ADDRESS_SPACE_PROGRAM, 16 )
 	AM_RANGE(0x000000, 0x07ffff) AM_ROM																	// ROM
 	AM_RANGE(0x080000, 0x083fff) AM_READWRITE(bigrun_vregs_r, bigrun_vregs_w) AM_BASE(&megasys1_vregs)	// Vregs
-	AM_RANGE(0x084000, 0x087fff) AM_WRITEONLY													// Linking with other units
+	AM_RANGE(0x084000, 0x087fff) AM_RAM													// Linking with other units
 	AM_RANGE(0x088000, 0x08bfff) AM_READWRITE(sharedram2_r, sharedram2_w) AM_BASE(&sharedram2)			// Sharedram with sub CPU#2
 	AM_RANGE(0x08c000, 0x08ffff) AM_READWRITE(sharedram1_r, sharedram1_w) AM_BASE(&sharedram1)			// Sharedram with sub CPU#1
 
@@ -623,7 +623,7 @@ ADDRESS_MAP_END
 
 static ADDRESS_MAP_START( bigrun_map3, ADDRESS_SPACE_PROGRAM, 16 )
 	AM_RANGE(0x000000, 0x03ffff) AM_ROM										// ROM
-	AM_RANGE(0x040000, 0x047fff) AM_READWRITE(sharedram2_r, sharedram1_w)	// Shared RAM (with Main CPU)
+	AM_RANGE(0x040000, 0x047fff) AM_READWRITE(sharedram2_r, sharedram2_w)	// Shared RAM (with Main CPU)
 	AM_RANGE(0x080000, 0x0807ff) AM_RAM AM_BASE(&cischeat_roadram[1])		// Road RAM
 	AM_RANGE(0x0c0000, 0x0c3fff) AM_RAM										// RAM
 ADDRESS_MAP_END
@@ -703,8 +703,8 @@ static ADDRESS_MAP_START( bigrun_sound_map, ADDRESS_SPACE_PROGRAM, 16 )
 	AM_RANGE(0x040000, 0x040001) AM_READWRITE(soundlatch_word_r, bigrun_soundbank_w)	// From Main CPU
 	AM_RANGE(0x060000, 0x060001) AM_WRITE(soundlatch2_word_w)							// To Main CPU
 	AM_RANGE(0x080000, 0x080003) AM_DEVREADWRITE8("ymsnd", ym2151_r, ym2151_w, 0x00ff)
-	AM_RANGE(0x0a0000, 0x0a0001) AM_DEVREADWRITE8("oki1", okim6295_r, okim6295_w, 0x00ff)
-	AM_RANGE(0x0c0000, 0x0c0001) AM_DEVREADWRITE8("oki2", okim6295_r, okim6295_w, 0x00ff)
+	AM_RANGE(0x0a0000, 0x0a0003) AM_DEVREADWRITE8("oki1", okim6295_r, okim6295_w, 0x00ff)
+	AM_RANGE(0x0c0000, 0x0c0003) AM_DEVREADWRITE8("oki2", okim6295_r, okim6295_w, 0x00ff)
 	AM_RANGE(0x0f0000, 0x0fffff) AM_RAM													// RAM
 ADDRESS_MAP_END
 
diff --git a/src/mame/drivers/speglsht.c b/src/mame/drivers/speglsht.c
index 04ff328e8e3..b52f0b0e1e2 100644
--- a/src/mame/drivers/speglsht.c
+++ b/src/mame/drivers/speglsht.c
@@ -202,6 +202,12 @@ static READ32_HANDLER(cop_r)
 	return 0;
 }
 
+static READ32_HANDLER(irq_ack_clear)
+{
+	cputag_set_input_line(space->machine, "sub", R3000_IRQ4, CLEAR_LINE);
+	return 0;
+}
+
 static ADDRESS_MAP_START( speglsht_mem, ADDRESS_SPACE_PROGRAM, 32 )
 	AM_RANGE(0x00000000, 0x000fffff) AM_RAM
 	AM_RANGE(0x01000000, 0x01007fff) AM_RAM //tested - STATIC RAM
@@ -214,7 +220,7 @@ static ADDRESS_MAP_START( speglsht_mem, ADDRESS_SPACE_PROGRAM, 32 )
 	AM_RANGE(0x01c00000, 0x01dfffff) AM_ROM AM_REGION("user2", 0)
 	AM_RANGE(0x0a000000, 0x0a003fff) AM_READWRITE(shared_r, shared_w)
 	AM_RANGE(0x1eff0000, 0x1eff001f) AM_RAM
-	AM_RANGE(0x1eff003c, 0x1eff003f) AM_READNOP //interrupt related
+	AM_RANGE(0x1eff003c, 0x1eff003f) AM_READ(irq_ack_clear)
 	AM_RANGE(0x1fc00000, 0x1fdfffff) AM_ROM AM_REGION("user1", 0)
 	AM_RANGE(0x2fc00000, 0x2fdfffff) AM_ROM AM_REGION("user1", 0) // mirror for interrupts
 ADDRESS_MAP_END
@@ -301,11 +307,6 @@ static const st0016_interface st0016_config =
 	&st0016_charram
 };
 
- static INTERRUPT_GEN( irq4_gen )
-{
-	cpu_set_input_line(device, R3000_IRQ4, ASSERT_LINE);
-}
-
 static const r3000_cpu_core config =
 {
 	0,
@@ -329,7 +330,7 @@ static MACHINE_DRIVER_START( speglsht )
 	MDRV_CPU_ADD("sub", R3000LE, 25000000)
 	MDRV_CPU_CONFIG(config)
 	MDRV_CPU_PROGRAM_MAP(speglsht_mem)
-	MDRV_CPU_VBLANK_INT("screen", irq4_gen)
+	MDRV_CPU_VBLANK_INT("screen", irq4_line_assert)
 
 	MDRV_QUANTUM_TIME(HZ(6000))
 	MDRV_MACHINE_RESET(speglsht)
diff --git a/src/mame/drivers/srmp5.c b/src/mame/drivers/srmp5.c
index 58c4d9cfff4..202e8777dda 100644
--- a/src/mame/drivers/srmp5.c
+++ b/src/mame/drivers/srmp5.c
@@ -336,6 +336,12 @@ static WRITE32_HANDLER(srmp5_vidregs_w)
 		logerror("vidregs write %08X %08X\n", offset << 2, state->vidregs[offset]);
 }
 
+static READ32_HANDLER(irq_ack_clear)
+{
+	cputag_set_input_line(space->machine, "sub", R3000_IRQ4, CLEAR_LINE);
+	return 0;
+}
+
 static ADDRESS_MAP_START( srmp5_mem, ADDRESS_SPACE_PROGRAM, 32 )
 	AM_RANGE(0x00000000, 0x000fffff) AM_RAM //maybe 0 - 2fffff ?
 	AM_RANGE(0x002f0000, 0x002f7fff) AM_RAM
@@ -362,7 +368,7 @@ static ADDRESS_MAP_START( srmp5_mem, ADDRESS_SPACE_PROGRAM, 32 )
 	AM_RANGE(0x0a200000, 0x0a3fffff) AM_READWRITE(tileram_r, tileram_w)
 
 	AM_RANGE(0x1eff0000, 0x1eff001f) AM_WRITEONLY
-	AM_RANGE(0x1eff003c, 0x1eff003f) AM_READNOP
+	AM_RANGE(0x1eff003c, 0x1eff003f) AM_READ(irq_ack_clear)
 	AM_RANGE(0x1fc00000, 0x1fdfffff) AM_ROM AM_REGION("user1", 0)
 	AM_RANGE(0x2fc00000, 0x2fdfffff) AM_ROM AM_REGION("user1", 0)
 ADDRESS_MAP_END
@@ -510,16 +516,6 @@ static const st0016_interface st0016_config =
 	&st0016_charram
 };
 
-//It seems that interrupt flags are never cleared, so I use last line only.
-
-static INTERRUPT_GEN( irq4_gen )
-{
-	if(cpu_getiloops(device) == 0)
-		cpu_set_input_line(device, R3000_IRQ4, ASSERT_LINE);
-	else
-		cpu_set_input_line(device, R3000_IRQ4, CLEAR_LINE);
-}
-
 static const r3000_cpu_core config =
 {
 	1,	/* 1 if we have an FPU, 0 otherwise */
@@ -569,8 +565,7 @@ static MACHINE_DRIVER_START( srmp5 )
 	MDRV_CPU_ADD("sub", R3000LE, 25000000)
 	MDRV_CPU_CONFIG(config)
 	MDRV_CPU_PROGRAM_MAP(srmp5_mem)
-	//256???K??
-	MDRV_CPU_VBLANK_INT_HACK(irq4_gen, 256)
+	MDRV_CPU_VBLANK_INT("screen", irq4_line_assert)
 
 	MDRV_QUANTUM_TIME(HZ(6000))