Implement Adjustable PowerPC Frequency (Underclocking)

[sgiannop]

To address the performance bottlenecks on Single Board Computers (SBCs) like the Raspberry Pi 5 and Android devices, we need to expose the internal PowerPC frequency as a Libretro Core Option. This allows users to trade cycle accuracy for a playable framerate.

Tasks:

• Add supermodel_ppc_frequency to the retro_variable array in libretro.cpp.
• Implement the following frequency options: Auto, 50, 66, 100, 133, 166, 200.
• Update update_core_options() to parse the selection and pass it to the emulator wrapper.
• Ensure the frequency change is applied during the PowerPC initialization phase.

[beudbeud]

i trying the commit and put at 50MHz and i still at 25~30fps

[sgiannop]

i trying the commit and put at 50MHz and i still at 25~30fps

@beudbeud could you pull and give it another spin ?

[beudbeud]

with last commit at 50Mhz still 25fps on virtual fighter 3 and sega rally 2

[sgiannop]

@beudbeud,
I've created a dev branch, to test some more aggressive performance optimizations, including:
Sound Toggle: (Disable sound to save CPU cycles)
Frame Skip: (0 to 3)
Ultra-low PPC Frequencies: (Down to 8MHz)

To test these, switch your local repo to the dev branch.

I’ve been testing these on my Android device (which, like the RPi 5, has limited resources).
By combining the PPC Frequency at 25MHz and Frame Skip 3, I managed to jump from 25 fps up to 35-40 fps.

While we aren't at a locked 60 fps yet, this is a significant improvement, though the frame jumping is definitely noticeable. I've also added a Sound Toggle - disabling sound can often free up just enough CPU cycles to stabilize the framerate. Give these a spin and let me know your results on the Pi 5.

[beudbeud]

With skip frame at 3 and PPC Frequencies at 25Mhz i feel i got some fps but is not enough for be playable.

With Recalbox when we add supermodel standalone for pi5 we got very similar problem because supermodel scale the render to the resolution of screen.

We do tricks for fix that we force resolution at 640 x 480 when we start supermodel.
So maybe need to find a way for not scale and stay on natif resolution (496 x 384)

[beudbeud]

i tried the last commiton dev branch and first on hdmi screen is totally not readable wehn you choose half resolution.

i see weird log when i start game

[INFO] [KMS] New FB: 1920x1080 (stride: 7680).
[INFO] [GLCore] Initializing HW render (2048x2048).
[INFO] [GLCore] Max texture size: 4096 px, renderbuffer size: 4096 px.
[INFO] [GLCore] Vendor: Broadcom, Renderer: V3D 7.1.7.0.
[INFO] [GLCore] Version: OpenGL ES 3.1 Mesa 25.1.0.
[INFO] [GLCore] Using resolution 1920x1080.

compare to a flycast

[INFO] [KMS] New FB: 1920x1080 (stride: 7680).
[INFO] [GLCore] Initializing HW render (1024x1024).
[INFO] [GLCore] Max texture size: 4096 px, renderbuffer size: 4096 px.
[INFO] [GLCore] Vendor: Broadcom, Renderer: V3D 7.1.7.0.
[INFO] [GLCore] Version: OpenGL ES 3.1 Mesa 25.1.0.
[INFO] [GLCore] Using resolution 1920x1080.

why supermodel init HW render at (2048x2048) even if is start in half internal resolution?

[beudbeud]

diff --git a/Src/OSD/libretro/libretro.cpp b/Src/OSD/libretro/libretro.cpp
index 0fa8368..af4c423 100644
--- a/Src/OSD/libretro/libretro.cpp
+++ b/Src/OSD/libretro/libretro.cpp
@@ -135,10 +135,11 @@ void retro_get_system_info(struct retro_system_info *info)
 
 void retro_get_system_av_info(struct retro_system_av_info *info)
 {
+   float multiplier = (g_options.resolution_multiplier > 0) ? g_options.resolution_multiplier : 1.0f;
    info->geometry.base_width   = 496;
    info->geometry.base_height  = 384;
-   info->geometry.max_width    = 496 * 4;
-   info->geometry.max_height   = 384 * 4;
+   info->geometry.max_width    = (unsigned)(496 * multiplier);
+   info->geometry.max_height   = (unsigned)(384 * multiplier);
    info->geometry.aspect_ratio = g_options.widescreen ? (16.0f / 9.0f) : (4.0f / 3.0f);
 
    info->timing.fps         = 57.53;
@@ -274,6 +275,16 @@ void retro_run(void)
       {
          last_width  = 0;
          last_height = 0;
+
+         struct retro_system_av_info av_info;
+         av_info.geometry.base_width   = 496;
+         av_info.geometry.base_height  = 384;
+         av_info.geometry.max_width    = (unsigned)(496 * g_options.resolution_multiplier);
+         av_info.geometry.max_height   = (unsigned)(384 * g_options.resolution_multiplier);
+         av_info.geometry.aspect_ratio = g_options.widescreen ? (16.0f / 9.0f) : (4.0f / 3.0f);
+         av_info.timing.fps            = 57.53;
+         av_info.timing.sample_rate    = 44100.0;
+         environ_cb(RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO, &av_info);
       }
 
       if (g_options.service_on_sticks != old_service_on_sticks)

with this patch game run at 50fps now on rpi5 with native resolution, frame skip 2