I got the game on sale and used the mega.nz patch listed above and it worked great! I'm running an i7 3930k which has 6 cores as well. Make sure to backup the original .exe and then delete it, and copy and paste the new one in. Thanks for the help guys.

Thanks. This is the fix I've been waiting many years for since I owned a 980X. Currently running a 6950X (10 core) and have had many >4 CPUs in between. Maybe now I'll finish the game.

I've sent a message to GOG support, by the way, about the fix and how it works.

I'm not really sure I went through the proper "channel" to reach support, because for some reason I always find it confusing, that is how to properly get in contact with GOG support about such matters (about a fix and not a bug). I have opened a ticket from the Support Center -> Contact Us -> Game Technical Issues form.

edit: just got a reply that it was forwarded to the appropriate GOG team!

Hopefully, this will become an official patch from GOG.

Pretty shameful to just sell the thing, without mentioning anything about these sorts of problems.

Every time I launch it, my computer crashes. Windows 8.1. And clearly, from the discussion, I'm not the only one.

Shame on you, GoG. This isn't the first game with which this has happened.

I downloaded the patch available through MEGA on page 2. Made Saboteur work for me with my Ryzen 1600. But since I got the patch my computer boots to BIOS and not to Windows and then have to exit and blah blah it gets me into Windows.
I'm pretty noob at the software side of computers - I just like playing the games hahahaha. I've deleted all trace of the patch file but I still can't boot directly to Windows. Anyone got a solution?

Sorry if it's a basic question, but I definitely appreciate any help anyone can offer. :)

The patch is not responsible for this issue you are having, something else is causing it.
You could probably check your motherboard manual or contact your motherboard's support for possible reasons that your PC can boot directly into BIOS menu without you triggering it.

Does it also reset your BIOS settings to default or is it just that it boots into BIOS?

It's been quite a few months now since GOG has put a clear warning in the game's store page. This thread is for the "more than 4 cores" issue. I hope that they will integrate the patch, so at least that issue goes away.

Clearly, from some other threads, people have also other issues with the game (probably like the crashes you mention), but those seem to be more isolated issues -- ie not everyone with Windows 8.1 has crashes, or with an old AMD GPU etc.

It just boots into BIOS; the settings have all stayed the same.
I just assumed it was the patch because it was the only thing I've downloaded/installed/updated this week, and it was only after that that I had the problems start. BUT! Thanks for clearing that up though, because at least now I know one thing that it isn't hahaha so I can rule that out.
Thanks heaps for your help.

Changed the Value at the address 0x9F56D0 from 0x76 to 0xEB and it still will not start... It doesn't even show up as a process.

What is your system configuration? CPU/ GPU / Operating System ?

It's indeed just one byte difference. See attached image for comparison. I just run it in Wine, and it works perfectly with that fix on my Ryzen 7 1700X (8 cores / 16 threads).

I made a simple script to patch the file in place using jackfuste's method above.
https://gist.github.com/shmerl/4458375a3529995ed6b41b1ce1718eeb

It must be only certain chips with more than 4 cores because my Origin version worked fine with my Phenom II and that was 6 core, but now I have a Ryzen with 8 cores and nada. Hopefully this 'fixed' executable y'all are muttering about will help.

This worked for me. Thanks.

Can confirm that Mega.NZ link does work, no issues there... now to fix the Xbone controller issue :P

Yeah just wanted to add to the confirmations - fix works perfectly - just remember that if you try to set refresh greater than 60hz, seems to revert the res back to 800 x 600 - which is no big issue cuz I dont think the game can handle greater than that.

GOG crew - please add this as a mandatory patch -

Thanks To all for this. I installed on 2 pc one with a 4 core 8 thread Ryzen no patch needed. But my Ryzen 6 core needed the patch. Thanks