Implement true CPU frequency scaling/overclocking

libretro.cpp

@@ -19,6 +19,7 @@
 #include "input.h"
 
 #include "mednafen/mednafen-endian.h"
+#include "mednafen/psx/psx.h"
 
 #include "../pgxp/pgxp_main.h"
 
@@ -47,6 +48,9 @@ bool cd_async = false;
 bool cd_warned_slow = false;
 int64 cd_slow_timeout = 8000; // microseconds
 
+// CPU overclock factor (or 0 if disabled)
+int32_t psx_overclock_factor = 0;
+
 // Sets how often (in number of output frames/retro_run invocations)
 // the internal framerace counter should be updated if
 // display_internal_framerate is true.
@@ -2673,6 +2677,24 @@ static void check_variables(bool startup)
    }
 #endif
 
+   var.key = option_cpu_freq_scale;
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+   {
+      int scale_percent = atoi(var.value);
+
+      if (scale_percent == 100) {
+         psx_overclock_factor = 0;
+      } else {
+         psx_overclock_factor = ((scale_percent << OVERCLOCK_SHIFT) + 50) / 100;
+      }
+   }
+   else
+      psx_overclock_factor = 0;
+
+   // Need to adjust the CPU<->GPU frequency ratio if the overclocking changes
+   GPU_RecalcClockRatio();
+
    var.key = option_gte_overclock;
 
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
@@ -3775,6 +3797,7 @@ void retro_set_environment(retro_environment_t cb)
 #endif
       { option_widescreen_hack, "Widescreen mode hack; disabled|enabled" },
       { option_frame_duping, "Frame duping (speedup); disabled|enabled" },
+      { option_cpu_freq_scale, "CPU frequency scaling (overclock); 100% (native)|110%|120%|130%|140%|150%|160%|170%|180%|190%|200%|300%|400%|500%|90%|80%|70%|60%|50%" },
       { option_gte_overclock, "GTE Overclock; disabled|enabled" },
       { option_skip_bios, "Skip BIOS; disabled|enabled" },
       { option_dither_mode, "Dithering pattern; 1x(native)|internal resolution|disabled" },

libretro_options.h

@@ -42,6 +42,7 @@
 #define option_multitap2             "beetle_psx_hw_enable_multitap_port2"
 #define option_mouse_sensitivity     "beetle_psx_hw_mouse_sensitivity"
 #define option_gun_cursor            "beetle_psx_hw_gun_cursor"
+#define option_cpu_freq_scale        "beetle_psx_hw_cpu_freq_scale"
 #define option_gte_overclock         "beetle_psx_hw_gte_overclock"
 #define option_cd_access_method      "beetle_psx_hw_cd_access_method"
 #define option_skip_bios             "beetle_psx_hw_skipbios"
@@ -79,6 +80,7 @@
 #define option_multitap2             "beetle_psx_enable_multitap_port2"
 #define option_mouse_sensitivity     "beetle_psx_mouse_sensitivity"
 #define option_gun_cursor            "beetle_psx_gun_cursor"
+#define option_cpu_freq_scale        "beetle_psx_cpu_freq_scale"
 #define option_gte_overclock         "beetle_psx_gte_overclock"
 #define option_cd_access_method      "beetle_psx_cd_access_method"
 #define option_skip_bios             "beetle_psx_skipbios"

mednafen/psx/cdc.cpp

@@ -146,6 +146,8 @@ int32 PS_CDC::CalcNextEvent(void)
 
    //fprintf(stderr, "%d %d %d %d --- %d\n", PSRCounter, PendingCommandCounter, CDCReadyReceiveCounter, DiscStartupDelay, next_event);
 
+   overclock_device_to_cpu(next_event);
+
    return(next_event);
 }
 
@@ -1122,6 +1124,8 @@ int32_t PS_CDC::Update(const int32_t timestamp)
 {
    int32 clocks = timestamp - lastts;
 
+   overclock_cpu_to_device(clocks);
+
    //doom_ts = timestamp;
 
    while(clocks > 0)

mednafen/psx/dma.cpp

@@ -511,6 +511,8 @@ static INLINE int32_t CalcNextEvent(int32_t next_event)
    if(DMACycleCounter < next_event)
       next_event = DMACycleCounter;
 
+   overclock_device_to_cpu(next_event);
+
    return(next_event);
 }
 
@@ -519,6 +521,9 @@ int32_t DMA_Update(const int32_t timestamp)
    int32_t clocks, i;
    //   uint32_t dc = (DMAControl >> (ch * 4)) & 0xF;
    clocks = timestamp - lastts;
+
+   overclock_cpu_to_device(clocks);
+
    lastts = timestamp;
 
    GPU_Update(timestamp);

mednafen/psx/frontio.cpp

@@ -470,8 +470,12 @@ int32_t FrontIO::CalcNextEventTS(int32_t timestamp, int32_t next_event)
       if(dsr_pulse_delay[i] > 0 && next_event > dsr_pulse_delay[i])
          next_event = dsr_pulse_delay[i];
 
+   overclock_device_to_cpu(next_event);
+
    ret = timestamp + next_event;
 
+   /* XXX Not sure if this is overclock-proof. This is probably only
+      useful for lightgun support however */
    if(irq10_pulse_ts[0] < ret)
       ret = irq10_pulse_ts[0];
 
@@ -700,13 +704,19 @@ int32_t FrontIO::Update(int32_t timestamp)
 
    clocks = timestamp - lastts;
 
+   overclock_cpu_to_device(clocks);
+
    for(i = 0; i < 4; i++)
       if(dsr_pulse_delay[i] > 0)
       {
          dsr_pulse_delay[i] -= clocks;
          if(dsr_pulse_delay[i] <= 0)
          {
-            dsr_active_until_ts[i] = timestamp + 32 + dsr_pulse_delay[i];
+            int32_t off = 32 + dsr_pulse_delay[i];
+
+            overclock_device_to_cpu(off);
+
+            dsr_active_until_ts[i] = timestamp + off;
             DoDSRIRQ();
          }
       }

mednafen/psx/gpu.cpp

@@ -630,10 +630,7 @@ void GPU_Init(bool pal_clock_and_tv,
       }
    }
 
-   if(GPU.HardwarePALType == false)  // NTSC clock
+   GPU_RecalcClockRatio();
-      GPU.GPUClockRatio = 103896; // 65536 * 53693181.818 / (44100 * 768)
-   else  // PAL clock
-      GPU.GPUClockRatio = 102948; // 65536 * 53203425 / (44100 * 768)
 
    memset(GPU.RGB8SAT_Under, 0, sizeof(GPU.RGB8SAT_Under));
 
@@ -651,6 +648,15 @@ void GPU_Init(bool pal_clock_and_tv,
    GPU.dither_upscale_shift = 0;
 }
 
+void GPU_RecalcClockRatio(void) {
+   if(GPU.HardwarePALType == false)  // NTSC clock
+      GPU.GPUClockRatio = 103896; // 65536 * 53693181.818 / (44100 * 768)
+   else  // PAL clock
+      GPU.GPUClockRatio = 102948; // 65536 * 53203425 / (44100 * 768)
+
+   overclock_cpu_to_device(GPU.GPUClockRatio);
+}
+
 void GPU_Destroy(void)
 {
    delete [] GPU.vram;

mednafen/psx/gpu.h

@@ -194,7 +194,7 @@ struct PS_GPU
    uint32 DotClockCounter;
 
    uint64 GPUClockCounter;
-   uint32 GPUClockRatio;
+   int32 GPUClockRatio;
    int32 LineClockCounter;
    int32 LinePhase;
 
@@ -247,6 +247,8 @@ void GPU_Init(bool pal_clock_and_tv,
 
 void GPU_SoftReset(void);
 
+void GPU_RecalcClockRatio(void);
+
 void GPU_Destroy(void);
 
 void GPU_Rescale(uint8 ushift);

mednafen/psx/psx.h

@@ -102,4 +102,31 @@ extern PS_CDC *CDC;
 extern PS_SPU *SPU;
 extern MultiAccessSizeMem<2048 * 1024, uint32_t, false> MainRAM;
 
+#define OVERCLOCK_SHIFT 8
+extern int32_t psx_overclock_factor;
+
+static INLINE void overclock_device_to_cpu(int32_t &clock) {
+   if (psx_overclock_factor) {
+      int64_t n = clock;
+
+      n = (n * psx_overclock_factor) + (1 << (OVERCLOCK_SHIFT)) - 1;
+
+      n >>= OVERCLOCK_SHIFT;
+
+      clock = n;
+   }
+}
+
+static INLINE void overclock_cpu_to_device(int32_t &clock) {
+   if (psx_overclock_factor) {
+      int64_t n = clock;
+
+      n = (n << OVERCLOCK_SHIFT) + (psx_overclock_factor - 1);
+
+      n /= psx_overclock_factor;
+
+      clock = n;
+   }
+}
+
 #endif

mednafen/psx/timer.cpp

@@ -113,7 +113,7 @@ static int32_t lastts;
 
 static uint32_t CalcNextEvent(void)
 {
-   uint32_t next_event = 1024; /**/
+   int32_t next_event = 1024; /**/
 
    unsigned i;
    for(i = 0; i < 3; i++)
@@ -154,6 +154,8 @@ static uint32_t CalcNextEvent(void)
          next_event = tmp_clocks;
    }
 
+   overclock_device_to_cpu(next_event);
+
    return(next_event);
 }
 
@@ -343,6 +345,8 @@ MDFN_FASTCALL int32_t TIMER_Update(const int32_t timestamp)
 {
    int32_t cpu_clocks = timestamp - lastts;
 
+   overclock_cpu_to_device(cpu_clocks);
+
    int32_t i;
    for(i = 0; i < 3; i++)
    {