Emulator Issues #11275
closedCurrent FPRF implementation seems to be non-deterministic between various x86-64 CPU Generations
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Description
Game Name?
F-Zero GX - GFZE01
Super Monkey Ball - GMBE8P
Super Monkey Ball 2 - GM2E8P
Likely other games using this engine
What's the problem? Describe what went wrong.
The game reports a desync when using FPRF
What steps will reproduce the problem?
Get two different CPUs and play an FPRF game. The first time FPRF is needed you'll get a desync.
Is the issue present in the latest development version? For future reference, please also write down the version number of the latest development version.
5.0-8370
Is the issue present in the latest stable version?
Unknown as testing this is a pain. Likely stems from the modern FPRF implementation which was 4.0-2729 or one of the optimizations that came after it to make games like F-Zero GX much faster. Because the blog is down right now I can't find it.
If I remember correctly there was a feature used on Haswell and newer CPUs to make it faster, and, I didn't used to have this issue with my Ivy Bridge playing with a sandy bridge, but, they may just be exceptions to the rule rather than some special CPU feature causing an issue. After all Sandy and Ivy aren't that different.
If your issue is a graphical issue, please attach screenshots and record a three frame fifolog of the issue if possible. Screenshots showing what it is supposed to look like from either console or older builds of Dolphin will help too. For more information on how to use the fifoplayer, please check here: https://wiki.dolphin-emu.org/index.php?title=FifoPlayer
What are your PC specifications? (CPU, GPU, Operating System, more)
In this test
PC1 - i7-6700K - GTX 1070 - Windows
PC2 - i7-7700K - GTX 1080 - Linux
Running two instances of F-Zero GX on either PC syncs fine. It only desyncs if we connect to eachother.
Is there anything else that can help developers narrow down the issue? (e.g. logs, screenshots,
configuration files, savefiles, savestates)
This is pretty insignificant compared to other issues, huh.