From 6c5b4293eba32d91d1342b74ec7ccb2d3b99f2eb Mon Sep 17 00:00:00 2001
From: Bart Trzynadlowski <bart.trzy@gmail.com>
Date: Sun, 14 Aug 2011 23:59:01 +0000
Subject: [PATCH] Musashi context is now cleared in M68KCtx constructor. The
 internal Musashi context is zeroed out initially but the dynamically
 allocated external contexts would sometimes be filled with garbage, which
 would trigger interrupts at the very first instruction after reset, making
 the 68K go off into the weeds. This fixes a nasty randomly-occurring bug I
 was seeing.

---
 Src/CPU/68K/68K.h             | 2 ++
 Src/CPU/68K/Musashi/m68kcpu.c | 4 ++++
 Src/Model3/DSB.cpp            | 3 ++-
 Src/Model3/SoundBoard.cpp     | 7 ++++++-
 Src/Sound/SCSP.cpp            | 2 +-
 5 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/Src/CPU/68K/68K.h b/Src/CPU/68K/68K.h
index 5395857..11c0802 100644
--- a/Src/CPU/68K/68K.h
+++ b/Src/CPU/68K/68K.h
@@ -32,6 +32,7 @@
 #ifndef INCLUDED_68K_H
 #define INCLUDED_68K_H
 
+#include <cstring>
 #include "Types.h"
 #include "Musashi/m68k.h"
 #include "CPU/Bus.h"
@@ -75,6 +76,7 @@ public:
 		Bus = NULL;
 		IRQAck = NULL;
 		musashiCtx = new unsigned char[m68k_context_size()];
+		memset(musashiCtx, 0, m68k_context_size());	// very important! garbage in context at reset can cause very strange bugs
 	}
 	
 	~SM68KCtx(void)
diff --git a/Src/CPU/68K/Musashi/m68kcpu.c b/Src/CPU/68K/Musashi/m68kcpu.c
index 670a06e..745321f 100644
--- a/Src/CPU/68K/Musashi/m68kcpu.c
+++ b/Src/CPU/68K/Musashi/m68kcpu.c
@@ -26,6 +26,10 @@
  *
  * Permission was obtained from Karl Stenerud to apply the GPL license to this
  * code.
+ *
+ * NOTE: The internal CPU context is initialized to all zeros here. If setting
+ * an external context for the first time, make sure it is cleared first, 
+ * otherwise interrupts may appear pending and other nasty problems.
  */
 
 /* ======================================================================== */
diff --git a/Src/Model3/DSB.cpp b/Src/Model3/DSB.cpp
index 7764fa8..5ed3fc2 100644
--- a/Src/Model3/DSB.cpp
+++ b/Src/Model3/DSB.cpp
@@ -1,4 +1,3 @@
-//TODO: DSB2 save states not working!
 //TODO: amp can print error messages -- change them to Supermodel error messages
 /**
  ** Supermodel
@@ -950,6 +949,7 @@ void CDSB2::RunFrame(INT16 *audioL, INT16 *audioR)
 {
 #ifdef SUPERMODEL_SOUND
 	M68KSetContext(&M68K);
+	//printf("DSB2 run frame PC=%06X\n", M68KGetPC());
 	
 	// While FIFO not empty...
 	while (fifoIdxR != fifoIdxW)
@@ -995,6 +995,7 @@ void CDSB2::Reset(void)
 	
 	M68KSetContext(&M68K);
 	M68KReset();
+	printf("DSB2 PC=%06X\n", M68KGetPC());
 	M68KGetContext(&M68K);
 	
 	DebugLog("DSB2 Reset\n");
diff --git a/Src/Model3/SoundBoard.cpp b/Src/Model3/SoundBoard.cpp
index 03001da..c16a72a 100644
--- a/Src/Model3/SoundBoard.cpp
+++ b/Src/Model3/SoundBoard.cpp
@@ -394,10 +394,15 @@ void CSoundBoard::Reset(void)
 	UpdateROMBanks();
 	M68KSetContext(&M68K);
 	M68KReset();
+	printf("SBrd PC=%06X\n", M68KGetPC());
 	M68KGetContext(&M68K);
 	if (NULL != DSB)
 		DSB->Reset();
 	DebugLog("Sound Board Reset\n");
+	printf("PC=%06X\n", M68KGetPC());
+	M68KSetContext(&M68K);
+	M68KGetContext(&M68K);
+	printf("PC=%06X\n", M68KGetPC());
 }
 
 void CSoundBoard::SaveState(CBlockFile *SaveState)
@@ -453,7 +458,7 @@ void CSoundBoard::AttachDSB(CDSB *DSBPtr)
 #define OFFSET_RAM2			(0x100000)	// 1 MB SCSP2 RAM
 #define OFFSET_AUDIO_LEFT	(0x200000)	// 1470 bytes (16 bits, 44.1 KHz, 1/60th second) left audio channel
 #define OFFSET_AUDIO_RIGHT	(0x2005BE)	// 1470 bytes right audio channel
-#define MEMORY_POOL_SIZE	(0x100000 + 0x100000 + 0x5be + 0x5be)
+#define MEMORY_POOL_SIZE	(0x100000+0x100000+0x5be+0x5be)
 
 BOOL CSoundBoard::Init(const UINT8 *soundROMPtr, const UINT8 *sampleROMPtr)
 {
diff --git a/Src/Sound/SCSP.cpp b/Src/Sound/SCSP.cpp
index fc78545..7b22eb6 100644
--- a/Src/Sound/SCSP.cpp
+++ b/Src/Sound/SCSP.cpp
@@ -1719,7 +1719,7 @@ void SCSP_DoMasterSamples(int nsamples)
 {
 	int slice=12000000/(SysFPS*nsamples);	// 68K cycles/sample
 	static int lastdiff=0;
-
+	
 	for(int s=0;s<nsamples;++s)
 	{
 		signed int smpl=0;