Working 2x overclocking (meepingsnesroms)

libretro/libretro.cpp

@@ -358,6 +358,7 @@ void retro_set_environment(retro_environment_t cb)
       { "nestopia_blargg_ntsc_filter", "Blargg NTSC filter; disabled|composite|svideo|rgb|monochrome" },
       { "nestopia_palette", "Palette; cxa2025as|consumer|canonical|alternative|rgb|pal|composite-direct-fbx|pvm-style-d93-fbx|ntsc-hardware-fbx|nes-classic-fbx-fs|raw|custom" },
       { "nestopia_nospritelimit", "Remove 8-sprites-per-scanline hardware limit; disabled|enabled" },
+      { "nestopia_overclock", "CPU Speed (Overclock); 1x|2x" },
       { "nestopia_fds_auto_insert", "Automatically insert first FDS disk on reset; enabled|disabled" },
       { "nestopia_overscan_v", "Mask Overscan (Vertical); enabled|disabled" },
       { "nestopia_overscan_h", "Mask Overscan (Horizontal); disabled|enabled" },
@@ -605,6 +606,16 @@ static void check_variables(void)
          video.EnableUnlimSprites(true);
    }
 
+   var.key = "nestopia_overclock";
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var))
+   {
+      if (strcmp(var.value, "1x") == 0)
+         video.EnableOverclocking(false);
+      else if (strcmp(var.value, "2x") == 0)
+         video.EnableOverclocking(true);
+   }
+
    var.key = "nestopia_fds_auto_insert";
 
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var))

source/core/NstApu.cpp

@@ -1961,6 +1961,7 @@ namespace Nes
 			dma.buffered       = false;
 			dma.address        = 0xC000;
 			dma.buffer         = 0x00;
+			overclockingIsSafe = true;
 		}
 
 		Cycle Apu::Dmc::GetResetFrequency(CpuModel model)
@@ -2174,16 +2175,31 @@ namespace Nes
 		{
 			out.dac = data & 0x7F;
 			curSample = out.dac * outputVolume;
+
+			if (out.dac != 0)
+			{
+				overclockingIsSafe = false;
+			}
 		}
 
 		NST_SINGLE_CALL void Apu::Dmc::WriteReg2(const uint data)
 		{
 			regs.address = 0xC000 | (data << 6);
+
+			if (regs.address != 0)
+			{
+				overclockingIsSafe = true;
+			}
 		}
 
 		NST_SINGLE_CALL void Apu::Dmc::WriteReg3(const uint data)
 		{
 			regs.lengthCounter = (data << 4) + 1;
+
+			if (regs.lengthCounter != 0)
+			{
+				overclockingIsSafe = true;
+			}
 		}
 
 		NST_SINGLE_CALL bool Apu::Dmc::ClockDAC()

source/core/NstApu.hpp

@@ -527,6 +527,8 @@ namespace Nes
 
 				Dmc();
 
+				bool overclockingIsSafe;
+
 				void Reset(CpuModel);
 				void UpdateSettings(uint);
 				void LoadState(State::Loader&,const Cpu&,CpuModel,Cycle&);
@@ -624,6 +626,16 @@ namespace Nes
 
 		public:
 
+			void SetOverclockSafety(bool safe)
+			{
+				dmc.overclockingIsSafe = safe;
+			}
+
+			bool GetOverclockSafety()
+			{
+				return dmc.overclockingIsSafe;
+			}
+
 			dword GetSampleRate() const
 			{
 				return settings.rate;

source/core/NstCpu.cpp

@@ -204,6 +204,8 @@ namespace Nes
 			ticks   = 0;
 			logged  = 0;
 
+			cpuOverclocking = false;
+
 			pc = RESET_VECTOR;
 
 			cycles.count  = 0;
@@ -1899,6 +1901,18 @@ namespace Nes
 
 			if (interrupt.irqClock != CYCLE_MAX)
 				interrupt.irqClock = (interrupt.irqClock > cycles.frame ? interrupt.irqClock - cycles.frame : 0);
+
+			if (cpuOverclocking)
+			{
+				uint startCycle = cycles.count;
+				uint lastCycle = cycles.count + extraCycles;
+				do
+				{
+					ExecuteOp();
+				}
+				while (cycles.count < extraCycles);
+				cycles.count = startCycle;
+			}
 		}
 
 		void Cpu::Clock()

source/core/NstCpu.hpp

@@ -487,6 +487,8 @@ namespace Nes
 			Ram ram;
 			Apu apu;
 			IoMap map;
+			bool cpuOverclocking;
+			uint extraCycles;
 
 			static dword logged;
 			static void (Cpu::*const opcodes[0x100])();
@@ -499,6 +501,12 @@ namespace Nes
 				return apu;
 			}
 
+			void SetOverclocking(bool overclocking,uint newCycles)
+			{
+				cpuOverclocking = overclocking;
+				extraCycles = newCycles;
+			}
+
 			Cycle Update(uint readAddress=0)
 			{
 				apu.ClockDMA( readAddress );

source/core/NstPpu.cpp

@@ -108,6 +108,7 @@ namespace Nes
 		yuvMap (NULL)
 		{
 			cycles.one = PPU_RP2C02_CC;
+			overclocked = false;
 			PowerOff();
 		}
 
@@ -555,6 +556,38 @@ namespace Nes
 					break;
 			}
 
+			if (overclocked)
+			{
+				Apu& audioSafeOverclock = cpu.GetApu();
+				if (audioSafeOverclock.GetOverclockSafety())
+				{
+					switch (model)
+					{
+						case PPU_RP2C02:
+						default:
+
+						cpu.SetOverclocking(true,PPU_RP2C02_HSYNC * PPU_RP2C02_VACTIVE);
+						break;
+
+						case PPU_RP2C07:
+
+						cpu.SetOverclocking(true,PPU_RP2C07_HSYNC * PPU_RP2C07_VACTIVE);
+						break;
+
+						case PPU_DENDY:
+
+						cpu.SetOverclocking(true,PPU_DENDY_HSYNC * PPU_DENDY_VACTIVE);
+						break;
+					}
+				}
+				else
+				{
+					cpu.SetOverclocking(false,0);
+				}
+
+				audioSafeOverclock.SetOverclockSafety(true);//overclocking is only safe if direct pcm audio has not been written for one frame
+			}
+
 			cpu.SetFrameCycles( frame );
 		}
 

source/core/NstPpu.hpp

@@ -416,6 +416,7 @@ namespace Nes
 			int scanline;
 			int scanline_sleep;
 			int ssleep;
+			bool overclocked;
 
 			PpuModel model;
 			Hook hActiveHook;
@@ -542,6 +543,16 @@ namespace Nes
 			{
 				return oam.spriteLimit;
 			}
+
+			bool GetOverclockState() const
+			{
+				return overclocked;
+			}
+
+			void SetOverclockState(bool overclock2x)
+			{
+				overclocked = overclock2x;
+			}
 		};
 	}
 }

source/core/api/NstApiVideo.cpp

@@ -58,6 +58,20 @@ namespace Nes
 			return RESULT_NOP;
 		}
 
+		Result Video::EnableOverclocking(bool state) throw()
+		{
+			if (emulator.tracker.IsLocked( true ))
+				return RESULT_ERR_NOT_READY;
+
+			if (emulator.ppu.GetOverclockState() != state)
+			{
+				emulator.ppu.SetOverclockState( state );
+				return RESULT_OK;
+			}
+
+			return RESULT_NOP;
+		}
+
 		bool Video::AreUnlimSpritesEnabled() const throw()
 		{
 			return !emulator.ppu.HasSpriteLimit();

source/core/api/NstApiVideo.hpp

@@ -223,6 +223,11 @@ namespace Nes
 			* @return result code
 			*/
 			Result EnableUnlimSprites(bool state) throw();
+
+			/**
+			* Adds extra scanlines to fix lag
+			*/
+			Result EnableOverclocking(bool state) throw();
 
 			/**
 			* Checks if the PPU sprite software extension is enabled.