Emulator Issues #13077
open
AArch64 and JIT64 cores do not synchronize on Netplay/TASes
Added by thomasalban about 2 years ago.
Updated about 2 years ago.
Relates to performance:
No
Relates to maintainability:
No
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!
- 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.
- 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.
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!
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).
Okay, well, the first thing to determine is if ghosts and user recorded replays are compatible between architectures.
The ghosts that come with the game sync for me.
- 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
Also available in: Atom
PDF
Updated by 
Updated by