Hello Guys,
I recently flashed my MSI X79 GD45 (8D) with a custom BIOS for NVME Support from here. Since I am rendering with an RTX3090 I wondered if this BIOS could be further modded to enable 4G Decoding and/or Resizeable BAR Support in BIOS? My RTX 3090 is not used as Display GPU. I am Running a Multi-GPU Setup without SLI.
The Bios I aquiered from here:
Regards
Jens 
So what gpu is used to boot? And what specific settings in Bio?
Hello thanks for the reply!
At the Moment an GTX 1660 Super is placed in PCI-E Slot 1 so I guess it is the one booting. It is also connected to the Monitor. BIOS is the most recent offical now again ME 8 Version E7760IMS.C80. The BIOS is running in pure UEFI, although when switching off the so called setting “Post in Fullscreen” the Windows Loading Screen is not shown in Full Resolution and occasinally switches to even more blurred CSM-Like representation. Since I already tried the first step for attaining ReBAR, switching the offset I extracted from the BIOS image to enable 4G decoding (its present, but hidden in BIOS). But PC is not booting after applying. When the System is booting only with one Card installed it boots and reacts to everything (keyboard) except that no Display is present. I assume some incompatibilty with loading the GOP correctly. Since the BIOS is “intuativetly restrictive” I already tried to switch the Access Tokens in .ROM and flash it; without any effect on unlocking hidden Settings.
Maybe I should add that I’am running an i7 4930k without iGPU.
Any thoughts on how to resolve this Issue?
Mostly in AMI 5 bioses the setings made with AMIBCP 5.x tool wont reflect as it needs changes in another bios module AMIsetupdata… yours should be a AMI Core IV and usually the tool works, but this could be the issue, in this cases only with IFRextract tool/Vars and hex edit.
Dont know how RU tool will react in this bios model.
Could you try these Bios?
E7760IMSMod.rar (5.1 MB)
.C82 above 4g disabled in amibcp
.C83 above 4g enbled in amibcp
or you could just use .C82 and do the changes you try, so with official bios, make all your settings done but not Above 4G Decode. just regular stuff you did set for your bios, then save oc profile to usb, save exit, then update the bios with the .C82 i sent, go to bios, load oc profile then save and exit. After that dump your whole bios using intel fpt -d bios.rom option, and start making changes (since you did load the oc profile from official bios, an loaded it to my modded bios, it should be fine as the full bios dump also have ur settings, like making it pure UEFI).
also did updated the ME of the bioses to 8.1.70.1590, you could flash it using intel fpt with -f -me biosname arguments if you want to update
Also try the grub method if you’re using .C82 bios(or ask @Kuri0 about this): Enabling hidden 4G decoding · xCuri0/ReBarUEFI Wiki · GitHub
The above 4g is present here:
