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Emulator Issues #11275

closed

Current FPRF implementation seems to be non-deterministic between various x86-64 CPU Generations

Added by JMC4789 over 5 years ago. Updated over 5 years ago.

Status:
Invalid
Priority:
Normal
Assignee:
-
% Done:

0%

Operating system:
N/A
Issue type:
Bug
Milestone:
Regression:
No
Relates to usability:
No
Relates to performance:
No
Easy:
No
Relates to maintainability:
No
Regression start:
Fixed in:

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.

Actions #1

Updated by JMC4789 over 5 years ago

  • Subject changed from Current FPRF implementation seems to be non-deterministic between various x86-64 CPU Architectures to Current FPRF implementation seems to be non-deterministic between various x86-64 CPU Generations
Actions #2

Updated by JMC4789 over 5 years ago

  • Status changed from New to Invalid

It appears we jumped the gun. This is not true. Sorry.

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