CPU: Memory access timings

src/core/bus.cpp

@@ -64,6 +64,11 @@ void Bus::Reset()
 
 bool Bus::DoState(StateWrapper& sw)
 {
+  sw.Do(&m_exp1_access_time);
+  sw.Do(&m_exp2_access_time);
+  sw.Do(&m_bios_access_time);
+  sw.Do(&m_cdrom_access_time);
+  sw.Do(&m_spu_access_time);
   sw.DoBytes(m_ram.data(), m_ram.size());
   sw.DoBytes(m_bios.data(), m_bios.size());
   sw.DoArray(m_MEMCTRL.regs, countof(m_MEMCTRL.regs));
@@ -223,7 +228,7 @@ void Bus::RecalculateMemoryTimings()
                 m_spu_access_time[2]);
 }
 
-bool Bus::DoInvalidAccess(MemoryAccessType type, MemoryAccessSize size, PhysicalMemoryAddress address, u32& value)
+TickCount Bus::DoInvalidAccess(MemoryAccessType type, MemoryAccessSize size, PhysicalMemoryAddress address, u32& value)
 {
   SmallString str;
   str.AppendString("Invalid bus ");
@@ -247,13 +252,16 @@ bool Bus::DoInvalidAccess(MemoryAccessType type, MemoryAccessSize size, Physical
   if (type == MemoryAccessType::Read)
     value = UINT32_C(0xFFFFFFFF);
 
-  return true;
+  return 1;
 }
 
-bool Bus::DoReadEXP1(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadEXP1(MemoryAccessSize size, u32 offset)
 {
   if (m_exp1_rom.empty())
-    return DoInvalidAccess(MemoryAccessType::Read, size, EXP1_BASE | offset, value);
+  {
+    // EXP1 not present.
+    return UINT32_C(0xFFFFFFFF);
+  }
 
   if (offset == 0x20018)
   {
@@ -264,10 +272,10 @@ bool Bus::DoReadEXP1(MemoryAccessSize size, u32 offset, u32& value)
   const u32 transfer_size = u32(1) << static_cast<u32>(size);
   if ((offset + transfer_size) > m_exp1_rom.size())
   {
-    value = UINT32_C(0);
-    return true;
+    return UINT32_C(0);
   }
 
+  u32 value;
   if (size == MemoryAccessSize::Byte)
   {
     value = ZeroExtend32(m_exp1_rom[offset]);
@@ -284,36 +292,32 @@ bool Bus::DoReadEXP1(MemoryAccessSize size, u32 offset, u32& value)
   }
 
   // Log_DevPrintf("EXP1 read: 0x%08X -> 0x%08X", EXP1_BASE | offset, value);
-  return true;
+  return value;
 }
 
-bool Bus::DoWriteEXP1(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteEXP1(MemoryAccessSize size, u32 offset, u32 value)
 {
-  return DoInvalidAccess(MemoryAccessType::Write, size, EXP1_BASE | offset, value);
+  Log_WarningPrintf("EXP1 write: 0x%08X <- 0x%08X", EXP1_BASE | offset, value);
 }
 
-bool Bus::DoReadEXP2(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadEXP2(MemoryAccessSize size, u32 offset)
 {
-  offset &= EXP2_MASK;
-
   // rx/tx buffer empty
   if (offset == 0x21)
   {
-    value = 0x04 | 0x08;
-    return true;
+    return 0x04 | 0x08;
   }
 
-  return DoInvalidAccess(MemoryAccessType::Read, size, EXP2_BASE | offset, value);
+  Log_WarningPrintf("EXP2 read: 0x%08X", EXP2_BASE | offset);
+  return UINT32_C(0xFFFFFFFF);
 }
 
-bool Bus::DoWriteEXP2(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteEXP2(MemoryAccessSize size, u32 offset, u32 value)
 {
-  offset &= EXP2_MASK;
-
   if (offset == 0x23)
   {
     if (value == '\r')
-      return true;
+      return;
 
     if (value == '\n')
     {
@@ -326,26 +330,26 @@ bool Bus::DoWriteEXP2(MemoryAccessSize size, u32 offset, u32 value)
       m_tty_line_buffer.AppendCharacter(Truncate8(value));
     }
 
-    return true;
+    return;
   }
 
   if (offset == 0x41)
   {
     Log_WarningPrintf("BIOS POST status: %02X", value & UINT32_C(0x0F));
-    return true;
+    return;
   }
 
-  return DoInvalidAccess(MemoryAccessType::Write, size, EXP2_BASE | offset, value);
+  Log_WarningPrintf("EXP2 write: 0x%08X <- 0x%08X", EXP2_BASE | offset, value);
 }
 
-bool Bus::DoReadMemoryControl(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadMemoryControl(MemoryAccessSize size, u32 offset)
 {
+  u32 value = m_MEMCTRL.regs[offset / 4];
   FixupUnalignedWordAccessW32(offset, value);
-  value = m_MEMCTRL.regs[offset / 4];
-  return true;
+  return value;
 }
 
-bool Bus::DoWriteMemoryControl(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteMemoryControl(MemoryAccessSize size, u32 offset, u32 value)
 {
   FixupUnalignedWordAccessW32(offset, value);
 
@@ -357,165 +361,151 @@ bool Bus::DoWriteMemoryControl(MemoryAccessSize size, u32 offset, u32 value)
     m_MEMCTRL.regs[index] = new_value;
     RecalculateMemoryTimings();
   }
-
-  return true;
 }
 
-bool Bus::DoReadMemoryControl2(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadMemoryControl2(MemoryAccessSize size, u32 offset)
 {
   if (offset == 0x00)
-  {
-    value = m_ram_size_reg;
-    return true;
-  }
+    return m_ram_size_reg;
 
-  return DoInvalidAccess(MemoryAccessType::Read, size, MEMCTRL2_BASE | offset, value);
+  u32 value = 0;
+  DoInvalidAccess(MemoryAccessType::Read, size, MEMCTRL2_BASE | offset, value);
+  return value;
 }
 
-bool Bus::DoWriteMemoryControl2(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteMemoryControl2(MemoryAccessSize size, u32 offset, u32 value)
 {
   if (offset == 0x00)
   {
     m_ram_size_reg = value;
-    return true;
+    return;
   }
 
-  return DoInvalidAccess(MemoryAccessType::Write, size, MEMCTRL2_BASE | offset, value);
+  DoInvalidAccess(MemoryAccessType::Write, size, MEMCTRL2_BASE | offset, value);
 }
 
-bool Bus::DoReadPad(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadPad(MemoryAccessSize size, u32 offset)
 {
-  value = m_pad->ReadRegister(offset);
-  return true;
+  return m_pad->ReadRegister(offset);
 }
 
-bool Bus::DoWritePad(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWritePad(MemoryAccessSize size, u32 offset, u32 value)
 {
   m_pad->WriteRegister(offset, value);
-  return true;
 }
 
-bool Bus::DoReadSIO(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadSIO(MemoryAccessSize size, u32 offset)
 {
   Log_ErrorPrintf("SIO Read 0x%08X", offset);
-  value = 0;
   if (offset == 0x04)
-    value = 0x5;
-
-  return true;
+    return 0x5;
+  else
+    return 0;
 }
 
-bool Bus::DoWriteSIO(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteSIO(MemoryAccessSize size, u32 offset, u32 value)
 {
   Log_ErrorPrintf("SIO Write 0x%08X <- 0x%08X", offset, value);
-  return true;
 }
 
-bool Bus::DoReadCDROM(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadCDROM(MemoryAccessSize size, u32 offset)
 {
   // TODO: Splitting of half/word reads.
   Assert(size == MemoryAccessSize::Byte);
-  value = ZeroExtend32(m_cdrom->ReadRegister(offset));
-  return true;
+  return ZeroExtend32(m_cdrom->ReadRegister(offset));
 }
 
-bool Bus::DoWriteCDROM(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteCDROM(MemoryAccessSize size, u32 offset, u32 value)
 {
   // TODO: Splitting of half/word reads.
   Assert(size == MemoryAccessSize::Byte);
   m_cdrom->WriteRegister(offset, Truncate8(value));
-  return true;
 }
 
-bool Bus::DoReadGPU(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadGPU(MemoryAccessSize size, u32 offset)
 {
   Assert(size == MemoryAccessSize::Word);
-  value = m_gpu->ReadRegister(offset);
-  return true;
+  return m_gpu->ReadRegister(offset);
 }
 
-bool Bus::DoWriteGPU(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteGPU(MemoryAccessSize size, u32 offset, u32 value)
 {
   Assert(size == MemoryAccessSize::Word);
   m_gpu->WriteRegister(offset, value);
-  return true;
 }
 
-bool Bus::DoReadMDEC(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadMDEC(MemoryAccessSize size, u32 offset)
 {
   Assert(size == MemoryAccessSize::Word);
-  value = m_mdec->ReadRegister(offset);
-  return true;
+  return m_mdec->ReadRegister(offset);
 }
 
-bool Bus::DoWriteMDEC(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteMDEC(MemoryAccessSize size, u32 offset, u32 value)
 {
   Assert(size == MemoryAccessSize::Word);
   m_mdec->WriteRegister(offset, value);
-  return true;
 }
 
-bool Bus::DoReadInterruptController(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadInterruptController(MemoryAccessSize size, u32 offset)
 {
+  u32 value = m_interrupt_controller->ReadRegister(offset);
   FixupUnalignedWordAccessW32(offset, value);
-  value = m_interrupt_controller->ReadRegister(offset);
-  return true;
+  return value;
 }
 
-bool Bus::DoWriteInterruptController(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteInterruptController(MemoryAccessSize size, u32 offset, u32 value)
 {
   FixupUnalignedWordAccessW32(offset, value);
   m_interrupt_controller->WriteRegister(offset, value);
-  return true;
 }
 
-bool Bus::DoReadTimers(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadTimers(MemoryAccessSize size, u32 offset)
 {
+  u32 value = m_timers->ReadRegister(offset);
   FixupUnalignedWordAccessW32(offset, value);
-  value = m_timers->ReadRegister(offset);
-  return true;
+  return value;
 }
 
-bool Bus::DoWriteTimers(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteTimers(MemoryAccessSize size, u32 offset, u32 value)
 {
   FixupUnalignedWordAccessW32(offset, value);
   m_timers->WriteRegister(offset, value);
-  return true;
 }
 
-bool Bus::DoReadSPU(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadSPU(MemoryAccessSize size, u32 offset)
 {
-  // 32-bit reads are read as two 16-bit writes.
+  // 32-bit reads are read as two 16-bit accesses.
   if (size == MemoryAccessSize::Word)
   {
     const u16 lsb = m_spu->ReadRegister(offset);
     const u16 msb = m_spu->ReadRegister(offset + 2);
-    value = ZeroExtend32(lsb) | (ZeroExtend32(msb) << 16);
+    return ZeroExtend32(lsb) | (ZeroExtend32(msb) << 16);
   }
   else
   {
-    value = ZeroExtend32(m_spu->ReadRegister(offset));
+    return ZeroExtend32(m_spu->ReadRegister(offset));
   }
-
-  return true;
 }
 
-bool Bus::DoWriteSPU(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteSPU(MemoryAccessSize size, u32 offset, u32 value)
 {
   // 32-bit writes are written as two 16-bit writes.
+  // TODO: Ignore if address is not aligned.
   if (size == MemoryAccessSize::Word)
   {
+    Assert(Common::IsAlignedPow2(offset, 2));
     m_spu->WriteRegister(offset, Truncate16(value));
     m_spu->WriteRegister(offset + 2, Truncate16(value >> 16));
-    return true;
+    return;
   }
 
+  Assert(Common::IsAlignedPow2(offset, 2));
   m_spu->WriteRegister(offset, Truncate16(value));
-  return true;
 }
 
-bool Bus::DoReadDMA(MemoryAccessSize size, u32 offset, u32& value)
+u32 Bus::DoReadDMA(MemoryAccessSize size, u32 offset)
 {
+  u32 value = m_dma->ReadRegister(offset);
   switch (size)
   {
     case MemoryAccessSize::Byte:
@@ -529,11 +519,10 @@ bool Bus::DoReadDMA(MemoryAccessSize size, u32 offset, u32& value)
       break;
   }
 
-  value = m_dma->ReadRegister(offset);
-  return true;
+  return value;
 }
 
-bool Bus::DoWriteDMA(MemoryAccessSize size, u32 offset, u32 value)
+void Bus::DoWriteDMA(MemoryAccessSize size, u32 offset, u32 value)
 {
   switch (size)
   {
@@ -552,5 +541,4 @@ bool Bus::DoWriteDMA(MemoryAccessSize size, u32 offset, u32 value)
   }
 
   m_dma->WriteRegister(offset, value);
-  return true;
 }

src/core/bus.h

@@ -40,7 +40,7 @@ public:
   bool WriteWord(PhysicalMemoryAddress address, u32 value);
 
   template<MemoryAccessType type, MemoryAccessSize size>
-  bool DispatchAccess(PhysicalMemoryAddress address, u32& value);
+  TickCount DispatchAccess(PhysicalMemoryAddress address, u32& value);
 
   void PatchBIOS(u32 address, u32 value, u32 mask = UINT32_C(0xFFFFFFFF));
   void SetExpansionROM(std::vector<u8> data);
@@ -93,6 +93,7 @@ private:
 
   enum : u32
   {
+    RAM_ACCESS_DELAY = 6,     // Nocash docs say RAM takes 6 cycles to access.
     MEMCTRL_REG_COUNT = 9
   };
 
@@ -148,51 +149,51 @@ private:
   void RecalculateMemoryTimings();
 
   template<MemoryAccessType type, MemoryAccessSize size>
-  bool DoRAMAccess(u32 offset, u32& value);
+  TickCount DoRAMAccess(u32 offset, u32& value);
 
   template<MemoryAccessType type, MemoryAccessSize size>
-  bool DoBIOSAccess(u32 offset, u32& value);
+  TickCount DoBIOSAccess(u32 offset, u32& value);
 
-  bool DoInvalidAccess(MemoryAccessType type, MemoryAccessSize size, PhysicalMemoryAddress address, u32& value);
+  TickCount DoInvalidAccess(MemoryAccessType type, MemoryAccessSize size, PhysicalMemoryAddress address, u32& value);
 
-  bool DoReadEXP1(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteEXP1(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadEXP1(MemoryAccessSize size, u32 offset);
+  void DoWriteEXP1(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadEXP2(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteEXP2(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadEXP2(MemoryAccessSize size, u32 offset);
+  void DoWriteEXP2(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadMemoryControl(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteMemoryControl(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadMemoryControl(MemoryAccessSize size, u32 offset);
+  void DoWriteMemoryControl(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadMemoryControl2(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteMemoryControl2(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadMemoryControl2(MemoryAccessSize size, u32 offset);
+  void DoWriteMemoryControl2(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadPad(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWritePad(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadPad(MemoryAccessSize size, u32 offset);
+  void DoWritePad(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadSIO(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteSIO(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadSIO(MemoryAccessSize size, u32 offset);
+  void DoWriteSIO(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadCDROM(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteCDROM(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadCDROM(MemoryAccessSize size, u32 offset);
+  void DoWriteCDROM(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadGPU(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteGPU(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadGPU(MemoryAccessSize size, u32 offset);
+  void DoWriteGPU(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadMDEC(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteMDEC(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadMDEC(MemoryAccessSize size, u32 offset);
+  void DoWriteMDEC(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadInterruptController(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteInterruptController(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadInterruptController(MemoryAccessSize size, u32 offset);
+  void DoWriteInterruptController(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadDMA(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteDMA(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadDMA(MemoryAccessSize size, u32 offset);
+  void DoWriteDMA(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadTimers(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteTimers(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadTimers(MemoryAccessSize size, u32 offset);
+  void DoWriteTimers(MemoryAccessSize size, u32 offset, u32 value);
 
-  bool DoReadSPU(MemoryAccessSize size, u32 offset, u32& value);
-  bool DoWriteSPU(MemoryAccessSize size, u32 offset, u32 value);
+  u32 DoReadSPU(MemoryAccessSize size, u32 offset);
+  void DoWriteSPU(MemoryAccessSize size, u32 offset, u32 value);
 
   CPU::Core* m_cpu = nullptr;
   DMA* m_dma = nullptr;
@@ -204,6 +205,8 @@ private:
   SPU* m_spu = nullptr;
   MDEC* m_mdec = nullptr;
 
+  std::array<TickCount, 3> m_exp1_access_time = {};
+  std::array<TickCount, 3> m_exp2_access_time = {};
   std::array<TickCount, 3> m_bios_access_time = {};
   std::array<TickCount, 3> m_cdrom_access_time = {};
   std::array<TickCount, 3> m_spu_access_time = {};

src/core/bus.inl

@@ -2,7 +2,7 @@
 #include "bus.h"
 
 template<MemoryAccessType type, MemoryAccessSize size>
-bool Bus::DoRAMAccess(u32 offset, u32& value)
+TickCount Bus::DoRAMAccess(u32 offset, u32& value)
 {
   // TODO: Configurable mirroring.
   offset &= UINT32_C(0x1FFFFF);
@@ -40,11 +40,12 @@ bool Bus::DoRAMAccess(u32 offset, u32& value)
     }
   }
 
-  return true;
+  // Nocash docs say RAM takes 6 cycles to access.
+  return RAM_ACCESS_DELAY;
 }
 
 template<MemoryAccessType type, MemoryAccessSize size>
-bool Bus::DoBIOSAccess(u32 offset, u32& value)
+TickCount Bus::DoBIOSAccess(u32 offset, u32& value)
 {
   // TODO: Configurable mirroring.
   if constexpr (type == MemoryAccessType::Read)
@@ -70,11 +71,11 @@ bool Bus::DoBIOSAccess(u32 offset, u32& value)
     // Writes are ignored.
   }
 
-  return true;
+  return m_bios_access_time[static_cast<u32>(size)];
 }
 
 template<MemoryAccessType type, MemoryAccessSize size>
-bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
+TickCount Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
 {
   if (address < 0x800000)
   {
@@ -86,8 +87,12 @@ bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
   }
   else if (address < (EXP1_BASE + EXP1_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadEXP1(size, address & EXP1_MASK, value) :
-                                              DoWriteEXP1(size, address & EXP1_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadEXP1(size, address & EXP1_MASK);
+    else
+      DoWriteEXP1(size, address & EXP1_MASK, value);
+
+    return m_exp1_access_time[static_cast<u32>(size)];
   }
   else if (address < MEMCTRL_BASE)
   {
@@ -95,39 +100,66 @@ bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
   }
   else if (address < (MEMCTRL_BASE + MEMCTRL_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadMemoryControl(size, address & PAD_MASK, value) :
-                                              DoWriteMemoryControl(size, address & PAD_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadMemoryControl(size, address & PAD_MASK);
+    else
+      DoWriteMemoryControl(size, address & PAD_MASK, value);
+
+    return 1;
   }
   else if (address < (PAD_BASE + PAD_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadPad(size, address & PAD_MASK, value) :
-                                              DoWritePad(size, address & PAD_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadPad(size, address & PAD_MASK);
+    else
+      DoWritePad(size, address & PAD_MASK, value);
+
+    return 1;
   }
   else if (address < (SIO_BASE + SIO_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadSIO(size, address & SIO_MASK, value) :
-                                              DoWriteSIO(size, address & SIO_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadSIO(size, address & SIO_MASK);
+    else
+      DoWriteSIO(size, address & SIO_MASK, value);
+
+    return 1;
   }
   else if (address < (MEMCTRL2_BASE + MEMCTRL2_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadMemoryControl2(size, address & PAD_MASK, value) :
-                                              DoWriteMemoryControl2(size, address & PAD_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadMemoryControl2(size, address & PAD_MASK);
+    else
+      DoWriteMemoryControl2(size, address & PAD_MASK, value);
+
+    return 1;
   }
   else if (address < (INTERRUPT_CONTROLLER_BASE + INTERRUPT_CONTROLLER_SIZE))
   {
-    return (type == MemoryAccessType::Read) ?
-             DoReadInterruptController(size, address & INTERRUPT_CONTROLLER_MASK, value) :
-             DoWriteInterruptController(size, address & INTERRUPT_CONTROLLER_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadInterruptController(size, address & INTERRUPT_CONTROLLER_MASK);
+    else
+      DoWriteInterruptController(size, address & INTERRUPT_CONTROLLER_MASK, value);
+
+    return 1;
   }
   else if (address < (DMA_BASE + DMA_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadDMA(size, address & DMA_MASK, value) :
-                                              DoWriteDMA(size, address & DMA_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadDMA(size, address & DMA_MASK);
+    else
+      DoWriteDMA(size, address & DMA_MASK, value);
+
+    return 1;
   }
   else if (address < (TIMERS_BASE + TIMERS_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadTimers(size, address & TIMERS_MASK, value) :
-                                              DoWriteTimers(size, address & TIMERS_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadTimers(size, address & TIMERS_MASK);
+    else
+      DoWriteTimers(size, address & TIMERS_MASK, value);
+
+    return 1;
   }
   else if (address < CDROM_BASE)
   {
@@ -135,18 +167,30 @@ bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
   }
   else if (address < (CDROM_BASE + GPU_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadCDROM(size, address & CDROM_MASK, value) :
-                                              DoWriteCDROM(size, address & CDROM_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadCDROM(size, address & CDROM_MASK);
+    else
+      DoWriteCDROM(size, address & CDROM_MASK, value);
+
+    return m_cdrom_access_time[static_cast<u32>(size)];
   }
   else if (address < (GPU_BASE + GPU_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadGPU(size, address & GPU_MASK, value) :
-                                              DoWriteGPU(size, address & GPU_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadGPU(size, address & GPU_MASK);
+    else
+      DoWriteGPU(size, address & GPU_MASK, value);
+
+    return 1;
   }
   else if (address < (MDEC_BASE + MDEC_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadMDEC(size, address & MDEC_MASK, value) :
-                                              DoWriteMDEC(size, address & MDEC_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadMDEC(size, address & MDEC_MASK);
+    else
+      DoWriteMDEC(size, address & MDEC_MASK, value);
+
+    return 1;
   }
   else if (address < SPU_BASE)
   {
@@ -154,8 +198,12 @@ bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
   }
   else if (address < (SPU_BASE + SPU_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadSPU(size, address & SPU_MASK, value) :
-                                              DoWriteSPU(size, address & SPU_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadSPU(size, address & SPU_MASK);
+    else
+      DoWriteSPU(size, address & SPU_MASK, value);
+
+    return m_spu_access_time[static_cast<u32>(size)];
   }
   else if (address < EXP2_BASE)
   {
@@ -163,8 +211,12 @@ bool Bus::DispatchAccess(PhysicalMemoryAddress address, u32& value)
   }
   else if (address < (EXP2_BASE + EXP2_SIZE))
   {
-    return (type == MemoryAccessType::Read) ? DoReadEXP2(size, address & EXP2_MASK, value) :
-                                              DoWriteEXP2(size, address & EXP2_MASK, value);
+    if constexpr (type == MemoryAccessType::Read)
+      value = DoReadEXP2(size, address & EXP2_MASK);
+    else
+      DoWriteEXP2(size, address & EXP2_MASK, value);
+
+    return m_exp2_access_time[static_cast<u32>(size)];
   }
   else if (address < BIOS_BASE)
   {

src/core/cpu_core.cpp

@@ -95,12 +95,16 @@ void Core::SetPC(u32 new_pc)
 bool Core::ReadMemoryByte(VirtualMemoryAddress addr, u8* value)
 {
   u32 temp = 0;
-  const bool result = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Byte>(addr, temp);
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Byte>(addr, temp);
   *value = Truncate8(temp);
-  if (!result)
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return true;
 }
 
 bool Core::ReadMemoryHalfWord(VirtualMemoryAddress addr, u16* value)
@@ -109,12 +113,16 @@ bool Core::ReadMemoryHalfWord(VirtualMemoryAddress addr, u16* value)
     return false;
 
   u32 temp = 0;
-  const bool result = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::HalfWord>(addr, temp);
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::HalfWord>(addr, temp);
   *value = Truncate16(temp);
-  if (!result)
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return true;
 }
 
 bool Core::ReadMemoryWord(VirtualMemoryAddress addr, u32* value)
@@ -122,21 +130,29 @@ bool Core::ReadMemoryWord(VirtualMemoryAddress addr, u32* value)
   if (!DoAlignmentCheck<MemoryAccessType::Read, MemoryAccessSize::Word>(addr))
     return false;
 
-  const bool result = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(addr, *value);
-  if (!result)
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(addr, *value);
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return true;
 }
 
 bool Core::WriteMemoryByte(VirtualMemoryAddress addr, u8 value)
 {
   u32 temp = ZeroExtend32(value);
-  const bool result = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Byte>(addr, temp);
-  if (!result)
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Byte>(addr, temp);
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return true;
 }
 
 bool Core::WriteMemoryHalfWord(VirtualMemoryAddress addr, u16 value)
@@ -145,11 +161,15 @@ bool Core::WriteMemoryHalfWord(VirtualMemoryAddress addr, u16 value)
     return false;
 
   u32 temp = ZeroExtend32(value);
-  const bool result = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::HalfWord>(addr, temp);
-  if (!result)
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::HalfWord>(addr, temp);
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return cycles;
 }
 
 bool Core::WriteMemoryWord(VirtualMemoryAddress addr, u32 value)
@@ -157,49 +177,53 @@ bool Core::WriteMemoryWord(VirtualMemoryAddress addr, u32 value)
   if (!DoAlignmentCheck<MemoryAccessType::Write, MemoryAccessSize::Word>(addr))
     return false;
 
-  const bool result = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Word>(addr, value);
-  if (!result)
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Word>(addr, value);
+  if (cycles < 0)
+  {
     RaiseException(Exception::DBE);
+    return false;
+  }
 
-  return result;
+  AddTicks(cycles - 1);
+  return true;
 }
 
 bool Core::SafeReadMemoryByte(VirtualMemoryAddress addr, u8* value)
 {
   u32 temp = 0;
-  const bool result = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Byte>(addr, temp);
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Byte>(addr, temp);
   *value = Truncate8(temp);
-  return result;
+  return (cycles >= 0);
 }
 
 bool Core::SafeReadMemoryHalfWord(VirtualMemoryAddress addr, u16* value)
 {
   u32 temp = 0;
-  const bool result = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::HalfWord>(addr, temp);
+  const TickCount cycles = DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::HalfWord>(addr, temp);
   *value = Truncate16(temp);
-  return result;
+  return (cycles >= 0);
 }
 
 bool Core::SafeReadMemoryWord(VirtualMemoryAddress addr, u32* value)
 {
-  return DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(addr, *value);
+  return DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(addr, *value) >= 0;
 }
 
 bool Core::SafeWriteMemoryByte(VirtualMemoryAddress addr, u8 value)
 {
   u32 temp = ZeroExtend32(value);
-  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Byte>(addr, temp);
+  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Byte>(addr, temp) >= 0;
 }
 
 bool Core::SafeWriteMemoryHalfWord(VirtualMemoryAddress addr, u16 value)
 {
   u32 temp = ZeroExtend32(value);
-  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::HalfWord>(addr, temp);
+  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::HalfWord>(addr, temp) >= 0;
 }
 
 bool Core::SafeWriteMemoryWord(VirtualMemoryAddress addr, u32 value)
 {
-  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Word>(addr, value);
+  return DoMemoryAccess<MemoryAccessType::Write, MemoryAccessSize::Word>(addr, value) >= 0;
 }
 
 void Core::Branch(u32 target)
@@ -235,10 +259,13 @@ void Core::RaiseException(Exception excode)
 
 void Core::RaiseException(Exception excode, u32 EPC, bool BD, bool BT, u8 CE)
 {
-  Log_DebugPrintf("Exception %u at 0x%08X (epc=0x%08X, BD=%s, CE=%u)", static_cast<u32>(excode),
-                  m_current_instruction_pc, EPC, BD ? "true" : "false", ZeroExtend32(CE));
 #ifdef Y_BUILD_CONFIG_DEBUG
-  DisassembleAndPrint(m_current_instruction_pc, 4, 0);
+  if (excode != Exception::INT && excode != Exception::Syscall && excode != Exception::BP)
+  {
+    Log_DebugPrintf("Exception %u at 0x%08X (epc=0x%08X, BD=%s, CE=%u)", static_cast<u32>(excode),
+                    m_current_instruction_pc, EPC, BD ? "true" : "false", ZeroExtend32(CE));
+    DisassembleAndPrint(m_current_instruction_pc, 4, 0);
+  }
 #endif
 
   m_cop0_regs.EPC = EPC;
@@ -499,8 +526,8 @@ void Core::Execute()
 {
   while (m_downcount >= 0)
   {
-    m_pending_ticks += 2;
-    m_downcount -= 2;
+    m_pending_ticks += 1;
+    m_downcount -= 1;
 
     // now executing the instruction we previously fetched
     m_current_instruction = m_next_instruction;
@@ -542,7 +569,7 @@ bool Core::FetchInstruction()
     RaiseException(Exception::AdEL, m_regs.npc, false, false, 0);
     return false;
   }
-  else if (!DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(m_regs.npc, m_next_instruction.bits))
+  else if (DoMemoryAccess<MemoryAccessType::Read, MemoryAccessSize::Word>(m_regs.npc, m_next_instruction.bits) < 0)
   {
     // Bus errors don't set BadVaddr.
     RaiseException(Exception::IBE, m_regs.npc, false, false, 0);

src/core/cpu_core.h

@@ -56,7 +56,7 @@ public:
 
 private:
   template<MemoryAccessType type, MemoryAccessSize size>
-  bool DoMemoryAccess(VirtualMemoryAddress address, u32& value);
+  TickCount DoMemoryAccess(VirtualMemoryAddress address, u32& value);
 
   template<MemoryAccessType type, MemoryAccessSize size>
   bool DoAlignmentCheck(VirtualMemoryAddress address);
@@ -75,6 +75,13 @@ private:
   bool InUserMode() const { return m_cop0_regs.sr.KUc; }
   bool InKernelMode() const { return !m_cop0_regs.sr.KUc; }
 
+  // timing
+  void AddTicks(TickCount ticks)
+  {
+    m_pending_ticks += ticks;
+    m_downcount -= ticks;
+  }
+
   void DisassembleAndPrint(u32 addr);
   void DisassembleAndPrint(u32 addr, u32 instructions_before, u32 instructions_after);
 

src/core/cpu_core.inl

@@ -6,7 +6,7 @@
 namespace CPU {
 
 template<MemoryAccessType type, MemoryAccessSize size>
-bool Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
+TickCount Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
 {
   switch (address >> 29)
   {
@@ -15,23 +15,17 @@ bool Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
       if constexpr (type == MemoryAccessType::Write)
       {
         if (m_cop0_regs.sr.Isc)
-          return true;
+          return 1;
       }
 
       const PhysicalMemoryAddress phys_addr = address & UINT32_C(0x1FFFFFFF);
       if ((phys_addr & DCACHE_LOCATION_MASK) == DCACHE_LOCATION)
       {
         DoScratchpadAccess<type, size>(phys_addr, value);
-        return true;
+        return 1;
       }
 
-      if (!m_bus->DispatchAccess<type, size>(phys_addr, value))
-      {
-        Panic("Bus error");
-        return false;
-      }
-
-      return true;
+      return m_bus->DispatchAccess<type, size>(phys_addr, value);
     }
 
     case 0x01: // KUSEG 512M-1024M
@@ -39,7 +33,7 @@ bool Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
     case 0x03: // KUSEG 1536M-2048M
     {
       // Above 512mb raises an exception.
-      return false;
+      return -1;
     }
 
     case 0x04: // KSEG0 - physical memory cached
@@ -47,36 +41,24 @@ bool Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
       if constexpr (type == MemoryAccessType::Write)
       {
         if (m_cop0_regs.sr.Isc)
-          return true;
+          return 1;
       }
 
       const PhysicalMemoryAddress phys_addr = address & UINT32_C(0x1FFFFFFF);
       if ((phys_addr & DCACHE_LOCATION_MASK) == DCACHE_LOCATION)
       {
         DoScratchpadAccess<type, size>(phys_addr, value);
-        return true;
+        return 1;
       }
 
-      if (!m_bus->DispatchAccess<type, size>(phys_addr, value))
-      {
-        Panic("Bus error");
-        return false;
-      }
-
-      return true;
+      return m_bus->DispatchAccess<type, size>(phys_addr, value);
     }
     break;
 
     case 0x05: // KSEG1 - physical memory uncached
     {
       const PhysicalMemoryAddress phys_addr = address & UINT32_C(0x1FFFFFFF);
-      if (!m_bus->DispatchAccess<type, size>(phys_addr, value))
-      {
-        Panic("Bus error");
-        return false;
-      }
-
-      return true;
+      return m_bus->DispatchAccess<type, size>(phys_addr, value);
     }
     break;
 
@@ -90,11 +72,11 @@ bool Core::DoMemoryAccess(VirtualMemoryAddress address, u32& value)
         else
           WriteCacheControl(value);
 
-        return true;
+        return 1;
       }
       else
       {
-        return false;
+        return -1;
       }
     }