Slowdowns only via Retroarch frontend for Kronos Saturn core

[gordonfreeman01]

Is there an existing issue for this?

• This is a bug in RetroArch frontend
• I have searched the existing issues

Description

The Kronos Saturn core via Retroarch frontend has reproducable slowdowns at specific in-game points in multiple games (e.g. Panzer Dragoon and Panzer Dragoon Zwei) irrespective of core and frontend video settings. This behaviour does not happen with the standalone Kronos 2.7.0 Windows emulator build from https://tradu-france.com/wiki-emu-compatibility/index.php?title=Accueil. The behaviour is similar to slowdowns seen here on the Beetle Saturn core (except that one was affecting FMVs which isn't the case here): #15426

Expected behavior

No slowdowns (as with standalone version).

Steps to reproduce the bug

1. Run a game, an easy one is Panzer Dragoon Zwei (which I'll use here)
2. Immediately after starting a new Panzer Dragoon Zwei game when the first level begins, as soon as the player assumes control a massive slowdown happens within seconds and then subsides
3. Slowdowns intermittently happen throughout the game at specific points (sometimes even affecting the BIOS screen when booting the game)

The log output below is from the above scenario until the slowdown is over and Retroarch is closed.

Version/Commit

1.21

Bisect Results

No response

Present in the nightly version

Yes, this is reproduced in the nightly build

Platform & operating system

Windows 10 22H2 64-bit

Affected Cores

Kronos

Environment information

No response

Relevant log output

[INFO] [Playlist]: Written to playlist file: "C:\RetroArch\content_history.lpl".
[INFO] [Core]: Using content: "C:\Games\Panzer Dragoon II Zwei (USA)\Panzer Dragoon II Zwei (USA).cue".
[INFO] [Core]: Content ran for a total of: 00 hours, 00 minutes, 00 seconds.
[INFO] [Core]: Unloading core..
[INFO] [Core]: Unloading core symbols..
[INFO] RetroArch 1.21.0 (Git 05f94af)
[INFO] === Build =======================================
[INFO] CPU Model Name: AMD Ryzen 7 5800X 8-Core Processor             
[INFO] Capabilities: MMX MMXEXT SSE SSE2 SSE3 SSSE3 SSE4 SSE42 AES AVX AVX2 
[INFO] Version: 1.21.0
[INFO] Git: 05f94af
[INFO] Built: Apr 30 2025
[INFO] =================================================
[INFO] [Input]: Found input driver: "dinput".
[INFO] [Core]: Loading dynamic libretro core from: "C:\RetroArch\cores\kronos_libretro.dll"
[INFO] [Overrides]: Redirecting save file to "C:\RetroArch\saves\Kronos\Panzer Dragoon II Zwei (USA).srm".
[INFO] [Overrides]: Redirecting save state to "C:\RetroArch\states\Kronos\Panzer Dragoon II Zwei (USA).state".
[INFO] [Environ]: GET_VFS_INTERFACE. Core requested version >= V1, providing V3.
[INFO] [Environ]: GET_CORE_OPTIONS_VERSION.
[INFO] [Environ]: GET_LANGUAGE: "0".
[INFO] [Environ]: RETRO_ENVIRONMENT_SET_CORE_OPTIONS_INTL.
[INFO] [Environ]: SET_CONTROLLER_INFO.
[INFO] [Environ]: GET_LOG_INTERFACE.
[INFO] [Environ]: GET_PERF_INTERFACE.
[INFO] [Environ]: SYSTEM_DIRECTORY: "C:\RetroArch\system".
[INFO] [Environ]: SAVE_DIRECTORY: "C:\RetroArch\saves\Kronos".
[INFO] [Environ]: PERFORMANCE_LEVEL: 16.
[INFO] [Environ]: SET_SERIALIZATION_QUIRKS.
[INFO] [Environ]: GET_DISK_CONTROL_INTERFACE_VERSION.
[INFO] [Environ]: SET_DISK_CONTROL_EXT_INTERFACE.
[INFO] [Content]: Content loading skipped. Implementation will load it on its own.
[INFO] [Environ]: SET_PIXEL_FORMAT: XRGB8888.
[INFO] [Environ]: GET_PREFERRED_HW_RENDER, video driver name: d3d11.
[INFO] [Environ]: GET_PREFERRED_HW_RENDER - Context callback set to RETRO_HW_CONTEXT_D3D11.
[INFO] [Environ]: SET_HW_RENDER, context type: glcore.
[INFO] Requesting core OpenGL context (4.3).
[INFO] [SRAM]: Skipping SRAM load.
[INFO] [Core]: Version of libretro API: 1, Compiled against API: 1
[INFO] [Core]: Geometry: 320x224, Aspect: 1.333, FPS: 60.00, Sample rate: 44100.00 Hz.
[INFO] [Video]: Set video size to: fullscreen.
[INFO] [Video]: Using HW render, glcore driver forced.
[INFO] [Video]: "glcore" saved as cached driver.
[INFO] [GLCore]: Found GL context: "wgl".
[INFO] [GLCore]: Detecting screen resolution: 3840x2160.
[INFO] [WGL]: Extensions: WGL_ARB_buffer_region WGL_ARB_create_context WGL_ARB_create_context_no_error WGL_ARB_create_context_profile WGL_ARB_create_context_robustness WGL_ARB_context_flush_control WGL_ARB_extensions_string WGL_ARB_make_current_read WGL_ARB_multisample WGL_ARB_pbuffer WGL_ARB_pixel_format WGL_ARB_pixel_format_float WGL_ARB_render_texture WGL_ATI_pixel_format_float WGL_EXT_colorspace WGL_EXT_create_context_es_profile WGL_EXT_create_context_es2_profile WGL_EXT_extensions_string WGL_EXT_framebuffer_sRGB WGL_EXT_pixel_format_packed_float WGL_EXT_swap_control WGL_EXT_swap_control_tear WGL_NVX_DX_interop WGL_NV_DX_interop WGL_NV_DX_interop2 WGL_NV_copy_image WGL_NV_delay_before_swap WGL_NV_float_buffer WGL_NV_multisample_coverage WGL_NV_multigpu_context WGL_NV_render_depth_texture WGL_NV_render_texture_rectangle 
[INFO] [WGL]: Adaptive VSync supported.
[INFO] [GLCore]: Initializing HW render (4096x4096).
[INFO] [GLCore]: Max texture size: 32768 px, renderbuffer size: 32768 px.
[INFO] [GLCore]: Vendor: NVIDIA Corporation, Renderer: NVIDIA GeForce RTX 4090/PCIe/SSE2.
[INFO] [GLCore]: Version: 4.6.0 NVIDIA 566.36.
[INFO] [GLCore]: Using resolution 3840x2160.
[INFO] [XInput]: Found XInput v1.4.
[INFO] [Joypad]: Found joypad driver: "xinput".
[INFO] [GLCore]: Loading stock shader.
[INFO] [slang]: Building pass #0 (N/A)
[INFO] [GLCore]: Not using frame history.
[INFO] [GLCore]: Not using framebuffer feedback.
[INFO] [Video]: Found display server: "win32".
[INFO] [Autoconf]: Xbox Series Controller configured in port 1.
[libretro INFO] Saturn Emulation mode
[INFO] [Environ]: SET_MEMORY_MAPS.
[INFO] [Environ]: SET_SUPPORT_ACHIEVEMENTS: yes.
[INFO] [Audio]: Set audio input rate to: 44100.00 Hz.
[INFO] [WASAPI]: Client initialized (shared, PCM, 48000Hz, 64.0ms).
[INFO] [Audio]: Started synchronous audio driver.
[INFO] [Microphone]: Initialized microphone driver.
[INFO] [Display]: Found display driver: "glcore".
[INFO] [MIDI]: Output device: "Microsoft GS Wavetable Synth".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_music_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_video_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_image_history.lpl".
[INFO] [Playlist]: Loading favorites file: "C:\RetroArch\content_favorites.lpl".
[INFO] [Environ]: SET_INPUT_DESCRIPTORS:
[INFO] [Environ]: SET_GEOMETRY: 1280x896, Aspect: 1.333.
[INFO] [Environ]: SET_GEOMETRY: 1408x896, Aspect: 1.333.
[INFO] [Environ]: SET_GEOMETRY: 2816x1792, Aspect: 1.333.
[INFO] [Environ]: SET_GEOMETRY: 1408x896, Aspect: 1.333.
[INFO] [Core]: Content ran for a total of: 00 hours, 00 minutes, 46 seconds.
[INFO] [Runtime]: Saving runtime log file: "C:\RetroArch\playlists\logs\Kronos\Panzer Dragoon II Zwei (USA).lrtl".
[INFO] [Video]: Restored video driver to "d3d11".
[INFO] [Core]: No content, starting dummy core.
[INFO] [Core]: Content ran for a total of: 00 hours, 00 minutes, 00 seconds.
[INFO] [Core]: Unloading game..
[INFO] [Core]: Unloading core..
[INFO] [Core]: Unloading core symbols..
[INFO] [Core]: Saved core options file to "C:\RetroArch\config\Kronos\Kronos.opt".
[INFO] RetroArch 1.21.0 (Git 05f94af)
[INFO] === Build =======================================
[INFO] CPU Model Name: AMD Ryzen 7 5800X 8-Core Processor             
[INFO] Capabilities: MMX MMXEXT SSE SSE2 SSE3 SSSE3 SSE4 SSE42 AES AVX AVX2 
[INFO] Version: 1.21.0
[INFO] Git: 05f94af
[INFO] Built: Apr 30 2025
[INFO] =================================================
[INFO] [Input]: Found input driver: "dinput".
[INFO] [Environ]: SET_PIXEL_FORMAT: RGB565.
[INFO] [Core]: Version of libretro API: 1, Compiled against API: 1
[INFO] [Core]: Geometry: 320x240, Aspect: 1.333, FPS: 60.00, Sample rate: 48000.00 Hz.
[INFO] [Video]: Set video size to: fullscreen.
[INFO] [XInput]: Found XInput v1.4.
[INFO] [Joypad]: Found joypad driver: "xinput".
[INFO] [Autoconf]: Xbox Series Controller configured in port 1.
[INFO] [D3D11]: Device created (Feature Level: 11.0)
[INFO] [D3D11]: Flip model and tear control supported and enabled.
[INFO] [D3D11]: Requesting 1 maximum frame latency, using 1.
[INFO] [D3D11]: Found GPU at index 0: "NVIDIA GeForce RTX 4090".
[INFO] [D3D11]: Found GPU at index 1: "Microsoft Basic Render Driver".
[INFO] [D3D11]: Using GPU index 0.
[INFO] [Video]: Found display server: "win32".
[INFO] [Audio]: Set audio input rate to: 48000.00 Hz.
[INFO] [WASAPI]: Client initialized (shared, PCM, 48000Hz, 64.0ms).
[INFO] [Audio]: Started synchronous audio driver.
[INFO] [Microphone]: Initialized microphone driver.
[INFO] [Display]: Found display driver: "d3d11".
[INFO] [MIDI]: Output device: "Microsoft GS Wavetable Synth".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_music_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_video_history.lpl".
[INFO] [Playlist]: Loading history file: "C:\RetroArch\content_image_history.lpl".
[INFO] [Playlist]: Loading favorites file: "C:\RetroArch\content_favorites.lpl".
[INFO] [Config]: Saved new config to "C:\RetroArch\retroarch.cfg".
[INFO] [Core]: Content ran for a total of: 00 hours, 00 minutes, 00 seconds.
[INFO] [Core]: Unloading core..
[INFO] [Core]: Unloading core symbols..

[hizzlekizzle]

This is most likely a core issue rather than a frontend issue, so it should probably go in the core's issue tracker: https://github.com/libretro/yabause/issues

Regardless, there's no guarantee that a libretro core will act exactly the same as the standalone program, especially where things like framedrops are concerned. I don't see any major/obvious issues from your log, but make sure you don't have any non-default settings enabled, especially ones like rewind or runahead.

[gordonfreeman01]

This is most likely a core issue rather than a frontend issue, so it should probably go in the core's issue tracker: https://github.com/libretro/yabause/issues

Regardless, there's no guarantee that a libretro core will act exactly the same as the standalone program, especially where things like framedrops are concerned. I don't see any major/obvious issues from your log, but make sure you don't have any non-default settings enabled, especially ones like rewind or runahead.

Thanks, I created libretro/yabause#314 there. I couldn't find the core's repo initially as the name is different since it's grouping several related cores, maybe an option to locate the repo from the frontend might be worth considering for bug reports. For the core, I've tried using default settings and didn't enable rewind as that is disabled for Kronos as it causes issues. Using the same settings on the standalone program has no issues hence why I thought it might be frontend-related.

[gordonfreeman01]

As per the latest on libretro/yabause#314, this seems to be a libretro API-related problem, likely caused by high OpenGL overhead since it doesn't affect standalone. Is there anything further I can do such as extended logs to help diagnose this?

[hizzlekizzle]

I think "high"/"huge" is a relative situation. The OpenGL overhead is usually pretty small, on the order of a few percent of FPS. If you can do any profiling, that might help pin down what's actually bottlenecking and where.

[gordonfreeman01]

I think "high"/"huge" is a relative situation. The OpenGL overhead is usually pretty small, on the order of a few percent of FPS. If you can do any profiling, that might help pin down what's actually bottlenecking and where.

Ok, what do I need to do to profile this, run renderdoc or enable some options to collect data in retroarch?

[hizzlekizzle]

Yeah, that sort of thing. I'm not an expert on profiling, myself.