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Emulator Issues #13077

open

AArch64 and JIT64 cores do not synchronize on Netplay/TASes

Added by thomasalban about 1 month ago. Updated 29 days ago.

Status:
Accepted
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

How to reproduce the issue:
Launch a netplay session on an M1 Mac (M1 pro macbook pro). Join the session with a windows pc. Launch Mario Kart Wii (PAL) and start a race. After a few seconds of the race, the desync between the clients will become such that it shows the other player driving into a wall when in reality they are driving normally. This is of course detrimental to Mario Kart Wii and many other games.
The issue can be fixed by launching dolphin using rosetta on the mac, however this causes performance issues. When testing this, both computers were on the latest beta version of dolphin.
I hope this can be resolved because otherwise dolphin is amazing on m1 macs!

Actions #1

Updated by JMC4789 about 1 month ago

  • Status changed from New to Won't fix

You're running Dolphin's JIT on two different architectures. The way instructions are reordered and whatnot mean that synchronization for netplay can't be guaranteed.

If something like the in-game replays aren't syncing (Like, ghosts in Mario Kart Wii) then there is a bug in one of the JITs causing the desyncs and that can be fixed. But if it's just a cycle accuracy issue that accumulates over a long period of time, there's not much we can do.

Actions #2

Updated by JosJuice about 1 month ago

  • Status changed from Won't fix to New

I don't agree that this is a Won't fix. It should be possible to make the two sync up. If the cycle counts aren't matching exactly between the two, that's a bug.

Actions #3

Updated by JMC4789 about 1 month ago

Oh okay. I just remember when we first got netplay together that you weren't targeting fixing the Desync Checker and figured this was the same.

Sorry!

Actions #4

Updated by JosJuice about 1 month ago

The problem is that it's really hard to figure out what's causing a given desync. But once the cause is figured out, the fix should be easy (comparatively speaking, at least).

Actions #5

Updated by JMC4789 about 1 month ago

Okay, well, the first thing to determine is if ghosts and user recorded replays are compatible between architectures.

Actions #6

Updated by JosJuice about 1 month ago

The ghosts that come with the game sync for me.

Actions #7

Updated by JMC4789 29 days ago

  • Subject changed from Netplay desync when playing with mac and windows to AArch64 and JIT64 cores do not synchronize on Netplay/TASes
  • Status changed from New to Accepted
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