Fixed cycle counting overflow that was causing DSB2 to halt execution.

Src/Model3/DSB.cpp

@@ -31,8 +31,6 @@
  * ---------
  * - Should MPEG_SetLoop() check for loopEnd==0? This causes crashes. Usually
  *   only occurs when loopStart is also 0, and that can only be checked here.
- * - Volume fade out in Daytona 2 is much too slow. Probably caused by 68K
- *	 timing or interrupts.
  * - Check actual MPEG sample rate. So far, all games seem to use 32 KHz, which
  *   may be a hardware requirement, but if other sampling rates are allowable,
  *   the code here will fail (it is hard coded for 32 KHz).
@@ -1017,27 +1015,28 @@ void CDSB2::RunFrame(INT16 *audioL, INT16 *audioR)
 
     M68KSetIRQ(1);	// indicate pending command
     //printf("68K INT fired\n");
-		m_totalCyclesElapsed += M68KRun(500);
+    m_cyclesElapsedThisFrame += M68KRun(500);
   }
 
-  // gm_matthew made the interesting discovery that IRQ2 may in fact be a timer interrupt
+  // Matthew Daniels made the interesting discovery that IRQ2 may in fact be a timer interrupt
   // rather than a per-frame interrupt.For Daytona 2 and Sega Rally 2, assuming a value
   // of 1KHz fixes music fade outs and some timing issues. It is very likely this is a
   // configurable timer and we should be on the look-out for games which appear to use
   // different values. It is equally likely that all games share a similar code base and
   // use 1KHz as the timer rate.
-  while (m_totalCyclesElapsed < m_nextFrameEndCycles)
+  while (m_cyclesElapsedThisFrame < k_framePeriod)
   {
-    if (m_totalCyclesElapsed >= m_nextTimerInterruptCycles)
+    if (m_cyclesElapsedThisFrame >= m_nextTimerInterruptCycles)
     {
       // Fire timer interrupt and schedule next one
       M68KSetIRQ(2);
-      m_nextTimerInterruptCycles = (m_totalCyclesElapsed + k_timerPeriod) - (m_totalCyclesElapsed + k_timerPeriod) % k_timerPeriod;
+      m_nextTimerInterruptCycles += k_timerPeriod;
     }
-    int cyclesToRun = (std::min)(m_nextTimerInterruptCycles, m_nextFrameEndCycles) - m_totalCyclesElapsed;
+    int cyclesToRun = (std::min)(m_nextTimerInterruptCycles, k_framePeriod) - m_cyclesElapsedThisFrame;
-    m_totalCyclesElapsed += M68KRun(cyclesToRun);
+    m_cyclesElapsedThisFrame += M68KRun(cyclesToRun);
   }
-  m_nextFrameEndCycles = (m_totalCyclesElapsed + k_framePeriod) - (m_totalCyclesElapsed + k_framePeriod) % k_framePeriod;
+  m_cyclesElapsedThisFrame -= k_framePeriod;
+  m_nextTimerInterruptCycles -= k_framePeriod;
 
   M68KGetContext(&M68K);
 
@@ -1097,8 +1096,7 @@ void CDSB2::Reset(void)
 	//printf("DSB2 PC=%06X\n", M68KGetPC());
 	M68KGetContext(&M68K);
 
-	m_totalCyclesElapsed = 0;
+	m_cyclesElapsedThisFrame = 0;
-	m_nextFrameEndCycles = k_framePeriod;
 	m_nextTimerInterruptCycles = k_timerPeriod;
 
 	DebugLog("DSB2 Reset\n");
@@ -1185,8 +1183,7 @@ void CDSB2::LoadState(CBlockFile *StateFile)
 
 	// Technically these should be saved/restored rather than being reset but that would mean
 	// the save state format has to be modified and the difference would be imperceptible anyway
-	m_totalCyclesElapsed = 0;
+	m_cyclesElapsedThisFrame = 0;
-	m_nextFrameEndCycles = k_framePeriod;
 	m_nextTimerInterruptCycles = k_timerPeriod;
 
 	// Restart MPEG audio at the appropriate position

Src/Model3/DSB.h

@@ -320,8 +320,7 @@ private:
 	M68KCtx	M68K;
 	static const int k_framePeriod = 4000000/60;
 	static const int k_timerPeriod = 4000000/1000; // 1KHz timer
-	int m_totalCyclesElapsed;
+	int m_cyclesElapsedThisFrame;
-	int m_nextFrameEndCycles;
 	int m_nextTimerInterruptCycles;
 };