Hello everyone,
wondering if this issue was still being looked at by someone?

This post made me remember about it.
https://x.com/lauriewired/status/2113322490219118804

Quite related according to https://github.com/FAForever/downlords-faf-client/pull/3504

`There’s a hidden dagger in almost every PC game from 1995-2005 that murders ARM processors.

It’s kind of an accident, and it all has to do with floating points.

x87 was Intel’s floating point extension to x86. I won’t get into all the historical drama, but Intel decided that all internal float math would be at 80-bit extended precision to reduce rounding errors.

Of course, today no one in their right mind uses 80-bit; standard 64-bit doubles are just too convenient. Modern ARM64 doesn’t have any 80-bit hardware!

This creates a nasty problem for emulation. How much x87 arithmetic can you replace with say, native ARM64 floating point (losing precision!) without breaking behavior?

It’s not so simple; dropping 16-bits of precision can cause funny physics glitches and such. But boy, if you need all 80-bits, the software fallback REALLY stinks.

With all the decomp/recomp hype lately, porting OG Xbox and PC games to mobile / ARM devices is extra tricky. Not impossible, but you’d be amazed at how much x87 code is in old games!`

On that note, did someone had the possibility to try running 2 FAF setups on M1 in a multiplayer game ?

We do know that between a Windows PC and a windows with emulation on M1 it does not work... but how about 2 identical emulated setups ?

@geosearchef Not sure what you're talking about here, you can perfectly play solo campaign, so yeah the M1 is perfectly fine. Problem is to do a multiplayer game or run a replay.

Not sure if there will ever be a way to mitigate that calculation discrepancy.

Do you think thee is a way around it? Or it is a lost cause.
I can use my setup to do some tests if needed, just keep in mind I'm not a developer myself so I may not have the tools you'd expect immediately at hand.

Another thing I'm curious about, I ran into the problem trying to game with friends that are on PC, none of them has a M1 mac, but how does it behave in a game between two M1 mac?

@dragun101 said in Does Supcom work with windows 11?:

We do legit have access to alot of the games' code. While not helpful for above problem I do think it is worth stressing that we do have alot going for other games don't.

hmmm, so you think that it would be possible to have a look into this matter?

I was thinking, it is probably a very naive thought but, can the calculation be done by another code, like a mod?
Or is it something that is done by a part that is untouchable?

@harzernoob said in Desync on all replays and games with Windows 11 Arm on M1 Max Apple:

@corsaire apparently I am quoted now for super low level debugging B).
If it is indeed due to some non deterministic part of the emulation microsoft might be able to fix it. But good luck getting them to trouble shoot it.

Well I just did that.
Chances are slim yeah, but hey, no harm in pointing out the discrepancy between x86-64 and emulated on arm64... Maybe with a bit of luck someone at Redmond will be interested.

One can hope

@jip That's a nice article you got here.
Interestingly it points to a possible solution for the case we are facing.

@sheikah
Couldn't it be possible to reinforce the code for those calculations to make them really identical?
I mean having two computers giving different results for a same calculation is kind of, bad.

Makes you remember the infamous Pentium processor floating point hardware bug...

Programs such as Matlab does tons of calculations and don't get throw out the windows whatever the processor or the OS that makes them run.

@corsaire said in Does Supcom work with windows 11?:

Does work on Windows11 on Mac M1 with the faf-client executable set on "Safe emulation"
https://docs.microsoft.com/en-us/windows/uwp/porting/apps-on-arm-program-compat-troubleshooter

One bit of advice however, it "works" but has a desynchonization problem.
See this topic https://forum.faforever.com/topic/2796/desync-on-all-replays-and-games-with-windows-11-arm-on-m1-max-apple/6