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SNES: SA1 - Added 5/6 cycle delay for math operations 

Reproduces the broken RPM counter in Race Drivin' SA1 hack (v1.1)
This commit is contained in:
Sour 2025-07-14 20:22:59 +09:00
parent 0761a6a9de
commit ed4cab750b
4 changed files with 32 additions and 13 deletions
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41
Core/SNES/Coprocessors/SA1/Sa1.cpp
View File

@ -197,21 +197,24 @@ void Sa1::Sa1RegisterWrite(uint16_t addr, uint8_t value)
case 0x2250:
//MCNT (Arithmetic Control)
ProcessMathOp();
_state.MathOp = (Sa1MathOp)(value & 0x03);
if(value & 0x02) {
//"Note: Writing Bit1=1 resets the sum to zero."
_state.MathOpResult = 0;
}
break;
case 0x2251: _state.MultiplicandDividend = (_state.MultiplicandDividend & 0xFF00) | value; break; //MA (Arithmetic parameters - Multiplicand/Dividend - Low)
case 0x2252: _state.MultiplicandDividend = (_state.MultiplicandDividend & 0x00FF) | (value << 8); break; //MA (Arithmetic parameters - Multiplicand/Dividend - High)
case 0x2253: _state.MultiplierDivisor = (_state.MultiplierDivisor & 0xFF00) | value; break; //MB (Arithmetic parameters - Multiplier/Divisor - Low)
case 0x2251: ProcessMathOp(); _state.MultiplicandDividend = (_state.MultiplicandDividend & 0xFF00) | value; break; //MA (Arithmetic parameters - Multiplicand/Dividend - Low)
case 0x2252: ProcessMathOp(); _state.MultiplicandDividend = (_state.MultiplicandDividend & 0x00FF) | (value << 8); break; //MA (Arithmetic parameters - Multiplicand/Dividend - High)
case 0x2253: ProcessMathOp(); _state.MultiplierDivisor = (_state.MultiplierDivisor & 0xFF00) | value; break; //MB (Arithmetic parameters - Multiplier/Divisor - Low)
case 0x2254:
ProcessMathOp();
//MB (Arithmetic parameters - Multiplier/Divisor - High)
_state.MultiplierDivisor = (_state.MultiplierDivisor & 0x00FF) | (value << 8);
//"Writing to 2254h starts the operation."
CalculateMathOpResult();
_state.MathStartClock = _cpu->GetCycleCount();
break;
case 0x2258:
@ -373,13 +376,13 @@ uint8_t Sa1::Sa1RegisterRead(uint16_t addr)
case 0x2304: break; //VCR (SA-1 V Counter read - Low)
case 0x2305: break; //VCR (SA-1 V Counter read - High)
case 0x2306: return _state.MathOpResult & 0xFF; //MR (Arithmetic result)
case 0x2307: return (_state.MathOpResult >> 8) & 0xFF; //MR (Arithmetic result)
case 0x2308: return (_state.MathOpResult >> 16) & 0xFF; break; //MR (Arithmetic result)
case 0x2309: return (_state.MathOpResult >> 24) & 0xFF; break; //MR (Arithmetic result)
case 0x230A: return (_state.MathOpResult >> 32) & 0xFF; break; //MR (Arithmetic result)
case 0x2306: ProcessMathOp(); return _state.MathOpResult & 0xFF; //MR (Arithmetic result)
case 0x2307: ProcessMathOp(); return (_state.MathOpResult >> 8) & 0xFF; //MR (Arithmetic result)
case 0x2308: ProcessMathOp(); return (_state.MathOpResult >> 16) & 0xFF; break; //MR (Arithmetic result)
case 0x2309: ProcessMathOp(); return (_state.MathOpResult >> 24) & 0xFF; break; //MR (Arithmetic result)
case 0x230A: ProcessMathOp(); return (_state.MathOpResult >> 32) & 0xFF; break; //MR (Arithmetic result)
case 0x230B: return _state.MathOverflow; break; //OF (Arithmetic overflow flag)
case 0x230B: ProcessMathOp(); return _state.MathOverflow; break; //OF (Arithmetic overflow flag)
case 0x230C: {
//VDP (Variable length data port - Low)
@ -643,9 +646,22 @@ void Sa1::IncVarLenPosition()
_state.VarLenCurrentBit &= 0x07;
}
void Sa1::CalculateMathOpResult()
void Sa1::ProcessMathOp()
{
if((int)_state.MathOp & (int)Sa1MathOp::Sum) {
if(_state.MathStartClock == 0) {
return;
}
bool sumMode = (int)_state.MathOp & (int)Sa1MathOp::Sum;
if(_cpu->GetCycleCount() - _state.MathStartClock < (sumMode ? 6 : 5)) {
//Still in-progress - do nothing for now
//TODO update result register/etc. clock by clock
return;
}
_state.MathStartClock = 0;
if(sumMode) {
uint64_t result = _state.MathOpResult + ((int16_t)_state.MultiplicandDividend * (int16_t)_state.MultiplierDivisor);
_state.MathOverflow = (result >> 33) & 0x80;
@ -858,6 +874,7 @@ void Sa1::Serialize(Serializer &s)
SV(_state.BitmapRegister2[4]); SV(_state.BitmapRegister2[5]); SV(_state.BitmapRegister2[6]); SV(_state.BitmapRegister2[7]);
SV(_state.CharConvDmaActive); SV(_state.CharConvBpp); SV(_state.CharConvFormat); SV(_state.CharConvWidth); SV(_state.CharConvCounter);
SV(_state.VarLenCurrentBit);
SV(_state.MathStartClock);
SV(_lastAccessMemType); SV(_openBus);
SVArray(_iRam, Sa1::InternalRamSize);

2
Core/SNES/Coprocessors/SA1/Sa1.h
View File

@ -49,7 +49,7 @@ private:
void UpdateSaveRamMappings();
void IncVarLenPosition();
void CalculateMathOpResult();
void ProcessMathOp();
void RunCharConvertType2();
void ProcessInterrupts();

1
Core/SNES/Coprocessors/SA1/Sa1Types.h
View File

@ -97,6 +97,7 @@ struct Sa1State
Sa1MathOp MathOp;
uint16_t MultiplicandDividend;
uint16_t MultiplierDivisor;
uint64_t MathStartClock;
uint64_t MathOpResult;
uint8_t MathOverflow;

1
UI/Interop/ConsoleState/SnesState.cs
View File

@ -673,6 +673,7 @@ public struct Sa1State
public Sa1MathOp MathOp;
public UInt16 MultiplicandDividend;
public UInt16 MultiplierDivisor;
public UInt64 MathStartClock;
public UInt64 MathOpResult;
public byte MathOverflow;