mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-27 10:38:46 -04:00
Alex Vanderveen
51 lines
2.0 KiB
Markdown
51 lines
2.0 KiB
Markdown
# SDL backends
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PSXRecomp uses SDL3 by default. A compatible system SDL3 package is preferred;
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otherwise CMake downloads the integrity-pinned SDL 3.4.10 release. To build the
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compatibility backend explicitly:
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```sh
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cmake -S . -B build-sdl2 -DPSX_SDL_BACKEND=SDL2
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```
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`PSX_SDL_BACKEND` accepts only `SDL3` or `SDL2`; it never silently changes the
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requested backend. `PSX_SDL3_FETCH=OFF` makes an SDL3 build system-package-only.
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## Initial Windows A/B exercise
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These measurements are smoke-level comparisons, not claims that one SDL
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generation makes emulation faster. Both builds used MinGW GCC 15.2, Release,
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static SDL, OpenBIOS, the OpenGL renderer, and a 165 Hz Windows host. Each row is
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three warmed runs of the runtime's frame-window diagnostic:
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| Game and workload | SDL3 wall time | SDL2 wall time | SDL3 difference |
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|---|---:|---:|---:|
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| Tomba 2, frames 60–660 | 9506.5 ± 10.9 ms | 9511.3 ± 19.0 ms | -0.05% |
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| Mega Man X6, frames 60–660 | 8174.0 ± 114.0 ms | 8199.2 ± 287.0 ms | -0.31% |
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Every Tomba 2 run executed exactly 928,243 dirty instructions and 309,407 dirty
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dispatches. Every Mega Man X6 run executed 3,962,702 dirty instructions and
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1,048,509 dirty dispatches. The paced wall-time differences are smaller than
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the observed variance, so the useful result is parity rather than a speed win.
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The SDL3 build was additionally exercised through:
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- the shared recomp-ui launcher event loop;
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- the SDL renderer presentation path (Tomba 2, 240 frames); and
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- the Vulkan renderer on an RTX 3080 Ti, including SDL3 instance-extension and
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surface creation APIs (Tomba 2, 240 frames).
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The repeatable diagnostic setup is:
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```sh
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PSX_RUNTIME_PERF_DIAG=1 \
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PSX_BENCH_WINDOW=60:660 \
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PSX_DEV_INPUT=0 \
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./game-runtime --no-launcher --disc /path/to/game.cue --renderer opengl
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```
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Compare only runs with identical frame windows and dirty instruction/dispatch
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counts. Warm each executable and disc image before collecting results; cold
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filesystem and overlay-capture state caused much larger swings than the SDL
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backend in the initial exercise.
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