Great, thanks for testing it. Now I’ve had more time to look at the vbios that makes sense. At first glance I assumed I’d just misunderstood how things work (normally a safe assumption!) so knowing it doesn’t actually work is a good thing, for me at least. The sad truth is this vBIOS was obviously from a very early prototype, it seems they’ve done just enough to get the internal screen working in MacOS, and nothing more.
EDIT: Does installing the display driver in Windows get the internal screen working ?
Still not sure how the prototype has a working DP when they're both broken on the 27" ??
The silver lining is that brightness control works, now we just need to understand why. My usual strategy would be to try and break it! I could send you a few different patched vbios to test some theories. There is a good chance we can get one DP output working, and there’s no risk of bricking the card, luckily they used a normal eeprom package instead of DFN so you can just recover it with the clip. Flashing it in windows would be easier if you can set up remote access first (Teamviewer). Thanks for everything you’ve done so far, let me know if you have time for some more tests.