From 8f5f2108b7b90ebfdb83a2567488b9ba0d728928 Mon Sep 17 00:00:00 2001
From: Barry Harris <44396066+barry65536@users.noreply.github.com>
Date: Tue, 6 May 2014 20:20:42 +0000
Subject: [PATCH] Actually interleave the CPUs in Battle Shark and update
 VBlank IRQ timing in Taito-Z driver

---
 src/burn/drv/taito/d_taitoz.cpp | 34 ++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/burn/drv/taito/d_taitoz.cpp b/src/burn/drv/taito/d_taitoz.cpp
index bf24054d5..3567f92f9 100644
--- a/src/burn/drv/taito/d_taitoz.cpp
+++ b/src/burn/drv/taito/d_taitoz.cpp
@@ -6412,7 +6412,8 @@ static void SpacegunDraw()
 
 static INT32 TaitoZFrame()
 {
-	INT32 nInterleave = TaitoFrameInterleave;
+	INT32 nInterleave = TaitoFrameInterleave;
+	INT32 nVBlankIRQFire = (INT32)(((double)256 / 271) * TaitoFrameInterleave);
 
 	if (TaitoReset) TaitoZDoReset();
 
@@ -6433,18 +6434,26 @@ static INT32 TaitoZFrame()
 		nTaitoCyclesSegment = nNext - nTaitoCyclesDone[nCurrentCPU];
 		nTaitoCyclesDone[nCurrentCPU] += SekRun(nTaitoCyclesSegment);
 		if (i == 10 && Sci && ((GetCurrentFrame() & 1) == 0)) SekSetIRQLine(6, SEK_IRQSTATUS_AUTO);
-		if (i == (TaitoFrameInterleave - 1)) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
+		if (i == nVBlankIRQFire) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
 		SekClose();
 		
 		// Run 68000 #2
-		if ((TaitoCpuACtrl & 0x01) && TaitoNumZ80s) {
-			nCurrentCPU = 1;
-			SekOpen(1);
-			nNext = (i + 1) * nTaitoCyclesTotal[nCurrentCPU] / nInterleave;
-			nTaitoCyclesSegment = nNext - nTaitoCyclesDone[nCurrentCPU];
-			nTaitoCyclesDone[nCurrentCPU] += SekRun(nTaitoCyclesSegment);
-			if (i == (TaitoFrameInterleave - 1)) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
-			SekClose();
+		if (TaitoNumZ80s) {
+			if (TaitoCpuACtrl & 0x01) {
+				nCurrentCPU = 1;
+				SekOpen(1);
+				nNext = (i + 1) * nTaitoCyclesTotal[nCurrentCPU] / nInterleave;
+				nTaitoCyclesSegment = nNext - nTaitoCyclesDone[nCurrentCPU];
+				nTaitoCyclesDone[nCurrentCPU] += SekRun(nTaitoCyclesSegment);
+				if (i == nVBlankIRQFire) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
+				SekClose();
+			}
+		} else {
+			nCurrentCPU = 1;
+			SekOpen(1);
+			BurnTimerUpdate(i * (nTaitoCyclesTotal[nCurrentCPU] / nInterleave));
+			if (i == nVBlankIRQFire) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
+			SekClose();
 		}
 		
 		if (TaitoNumZ80s) {
@@ -6460,10 +6469,9 @@ static INT32 TaitoZFrame()
 		if (pBurnSoundOut) BurnYM2610Update(pBurnSoundOut, nBurnSoundLen);
 		ZetClose();
 	} else {
-		SekOpen(1);
-		if (TaitoCpuACtrl & 0x01) BurnTimerEndFrame(nTaitoCyclesTotal[1]);
+		SekOpen(1);
+		if (TaitoCpuACtrl & 0x01) BurnTimerEndFrame(nTaitoCyclesTotal[1]);
 		if (pBurnSoundOut) BurnYM2610Update(pBurnSoundOut, nBurnSoundLen);
-		if (TaitoCpuACtrl & 0x01) SekSetIRQLine(TaitoIrqLine, SEK_IRQSTATUS_AUTO);
 		SekClose();
 	}