100% mismatch rate when playing Zero Hour online using Silicon-based Mac (with Windows 11 VM)

[nhatter]

Area(s) with this issue?

The bug also exists in the Zero Hour Expansion Pack

Describe the issue

I have two Macbooks, both running Parallels Desktop virtual machine:

Intel-based Macbook
One is a 2014 Intel-based Macbook with Windows 10 VM - it plays Zero Hour absolutely fine, I play for at least an hour or so every day, almost every day. Zero Hour does get mismatch occasionally, but no more than other players.

Silicon-based (M-Series) Macbook
The other is a 2024 Silicon-based (ARM64) M4 Macbook with Windows 11 VM - and it does play Zero Hour off-line perfectly (and with superb graphics). But every time I've tried to play online, Zero Hour gives the mismatch error at the start of the game, 100% of the time, without fail.

I've heard that this may be because of minor differences in floating point logic of Silicon-based macs perhaps.

(Note: this could be useful for testing, as I can trigger mismatch 100% of the time with the M4 Macbook - happy to be a tester of any mismatch solutions!)

And yes, I've tried GenPatcher fixes, GenTool, compatibility modes, run as administrator etc. I've also tried disabling firewall, Windows Defender, and also doing a rain dance and summoning Cthulhu. Nothing seems to fix the 100% mismatch on the M4 Macbook.

Steps to reproduce

1. Save up a couple of thousands bucks
2. Buy an M-series Macbook (eg. M4)
3. Install Parallels Desktop with a Windows 11 VM
4. Try to play an online game of Zero Hour (v1.04) using the Direct Connect feature (eg. via GameRanger)
5. Game will mismatch 100% of the time at the start of the game

Attachments

No response

[tintinhamans]

1. Save up a couple of thousands bucks
2. Buy an M-series Macbook (eg. M4)

🤣

[nhatter]

1. Save up a couple of thousands bucks
2. Buy an M-series Macbook (eg. M4)

🤣

Yeah, those new series Macbooks, they're not cheap ;) But they are pretty powerful. My M4 has like 16 GPU cores. It runs Generals so well compared to my crusty Intel-based Macbook (which has to run the game on lowest settings especially when there's many units in online games).

Would love to be able to finally use my M4 powerhouse to play Generals online :)

[nhatter]

@tintinhamans - shouldn't this issue be marked as "bug" on issue type? Saw was marked as feature.

But thanks for marking as major anyway :) Agreed, it is major, it's making it hard for players with newer Macs to be able to play the game online...

[xmesaj2]

This sounds more like parallels issue because the game works fine under win11 and linux via wine with d3d8 native override & emulated virtual desktop

[OmniBlade]

This is almost certainly related to how CPU instructions are virtualised for floating point operations and realistically there is little we can do regards compatibility short term. Longer term if we can get cross platform lock step working this issue should go away because we'll hopefully get to macOS native builds.

[nhatter]

Yeah several people have said that. While native macOS builds would be nice again (ZH used to be on Mac App Store) priority should be fixing game crashes and mismatches should come first. Once those are fixed, at the very least, should be able to play on a virtual machine.

…

On Wednesday, 12 March 2025, OmniBlade ***@***.***> wrote: This is almost certainly related to how CPU instructions are virtualised for floating point operations and realistically there is little we can do regards compatibility short term. Longer term if we can get cross platform lock step working this issue should go away because we'll hopefully get to macOS native builds. — Reply to this email directly, view it on GitHub <#397 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AASJY56MCI4UFKZ56R3FMYL2T74MFAVCNFSM6AAAAABYTGWMA2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDOMJXGIYDCMZZG4> . You are receiving this because you authored the thread.Message ID: ***@***.***> [image: OmniBlade]*OmniBlade* left a comment (TheSuperHackers/ GeneralsGameCode#397) <#397 (comment)> This is almost certainly related to how CPU instructions are virtualised for floating point operations and realistically there is little we can do regards compatibility short term. Longer term if we can get cross platform lock step working this issue should go away because we'll hopefully get to macOS native builds. — Reply to this email directly, view it on GitHub <#397 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AASJY56MCI4UFKZ56R3FMYL2T74MFAVCNFSM6AAAAABYTGWMA2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDOMJXGIYDCMZZG4> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[OmniBlade]

Except the fix to mismatches due to differences in platform float implementation IS to get cross platform float consistency which comes as part of the cross platform work. If parallels can't or won't implement float instructions to produce binary matching results with a real x87 fpu, nothing we do can make that work other than making a native implemention that matches everywhere.

[augustresende]

Related discussion about root causes of this kind of mismatches: #369

[nhatter]

Attached an instant mismatch from a 1v1 game (happens about 9 seconds in). Both running on same network, with v1.04 and Gentool.

Client 1: Windows 10 (Parallels Desktop VM on Intel-based Macbook, v1.04 + Gentool)
Client 2: Windows 11 (Parallels Desktop VM on Silicon-based Macbook, v1.04 + Gentool)

Might be helpful for debugging.

Instant Mismatch.zip