Missing 4G decoding on Gigabyte GA-X99-UD4

[alexnur]

MOBO: Gigabyte GA-X99-UD4 rev. 1.1
BIOS: F23.
CPU: Intel Xeon E5-2685 v4
GPU: Nvidia Tesla V100, 6600GT
CSM disabled, SecureBoot enabled, TPM 2.0 Enabled

Yesterday I installed a video card nVidia Tesla V100 with 16 GB of video memory. The computer turns on, hums with fans and turns off after 30 seconds (sometimes it reboots). I pulled out the video card V100 - everything is fine. The reason for this may be the lack of the "Above 4G" option in the BIOS

Im curious to check if Re-Bar can work on my motherboard using this instruction:
https://github.com/xCuri0/ReBarUEFI/wiki/Enabling-hidden-4G-decoding

Im stuck on 4 step. I find 4G Decod using UEFITOOL, extracted body, next i used [IRFExtractor_0.6.0 and IRFExtractor_v1.5.1] to save output file.
Output file doesn't contain "4G Decod".

However, I found the following fragment in the text file:
OneOf Prompt: "PFMMIO 64 bit Resources Padding", Help: "Padd PCI MMIO 64-bit Prefetchable Resources behind the bridge for Hot-Plug.", QuestionFlags: 0x10, QuestionId: 0x208, VarStoreId: 0x1, VarOffset: 0x4B2, Flags: 0x11, Size: 16, Min: 0x0, Max: 0x2000, Step: 0x0
OneOfOption Option: "Disabled" Value: 0, Default
OneOfOption Option: "1 M" Value: 1
OneOfOption Option: "2 M" Value: 2
OneOfOption Option: "4 M" Value: 4
OneOfOption Option: "8 M" Value: 8
OneOfOption Option: "16 M" Value: 16
OneOfOption Option: "32 M" Value: 32
OneOfOption Option: "64 M" Value: 64
OneOfOption Option: "128 M" Value: 128
OneOfOption Option: "256 M" Value: 256
OneOfOption Option: "512 M" Value: 512
OneOfOption Option: "1 G" Value: 1024
OneOfOption Option: "2 G" Value: 2048
OneOfOption Option: "4 G" Value: 4096
OneOfOption Option: "8 G" Value: 8192
End

That's it "Above 4G"?

[alexnur]

mb_bios_ga-x99-ud4_f23.zip
Attach BIOS file

[xCuri0]

Likely duplicate of #14 but will keep this open because it's a different chipset.

[davidfchuck]

I just luckily fell into the fix for this. I ordered a Giga X99 UD4 for LLM testing with Mi50's. It came shipped with BIOS v. F22 on it. I was surprised when I saw "Enable 4G Decoding" in the bios menu as I'd been informed this mobo didn't offer it / couldn't boot the Mi50's. I'd been working on the ASUS X99-e WS.

For another reason (trying to get XMP to 2666) I installed the latest BIOS 24c, and low and behold "Enable 4G Decoding" is no longer an option in BIOS!

SOLUTION: roll your BIOS back to ver. F22. Enable 4G is available here.

I'm successfully booting two Mi50's and a single Radeon Vii on the board now... in x16, x16, x8 config. And running Llama.cpp on it quite well. ***edit. I also set the PCIE to Gen3, not Auto. And enabled virtualization... that latter one likely doesn't matter. But I'm booting successfully. I don't have access to Bios splash screen anymore, but Ubuntu 24 boots right up. To fix, I likely have to set the "Initial Display" to PCIE 3, as that's where my Radeon 7 is located.

I'll be posting a video on this shortly. I don't have a link generated yet... I'm still filming content.
But here's my channel: youtube.com/@CountryBoyComputers