[Request] vBIOS mod to fix Radeon 5600XT ReBAR support (max.: 8 GB)

BIOS/UEFI Modding BIOS modules (PCI ROM, EFI and others)
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To make a long history short…

Radeons 5600XT from multiple vendors (Perhaps all, but can confirm on my own MSI Gaming X and Sapphire Pulse based on other report) return these supported ReBAR capabilities via lspci -vvv under Linux:

03:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 [Radeon RX 5600 OEM/5600 XT / 5700/5700 XT] [1002:731f] (rev ca) (prog-if 00 [VGA controller])
Capabilities: [200 v1] Physical Resizable BAR
BAR 0: current size: 8GB, supported: 256MB 512MB 1GB
BAR 2: current size: 2MB, supported: 2MB 4MB 8MB 16MB 32MB 64MB 128MB 256MB

The 1 GiB is the highest one, and is what Windows 11 uses when ReBAR is On on BIOS Setup:

But, if you paid attention to lspci output above, it reports than the CURRENT BAR0 size is 8 GiB. After some googling I found than an AMD engineer upstreamed a commit to some Linux component saying than GPUs with Device ID 0x731F (Which seems to be ALL Radeons 5600XT) ReBAR Capabilities announcement is broken, but they can force the 8 GiB value just fine:

The AMD engineer mentioned than “This is most likely fixable with a VBIOS update”, but as far that I could google this never materialized, so 5600XT is stuck with 1 GiB ReBAR in Windows because that is the maximum announced. In comparison, the 5700XT I saw do properly announce 8 GiB ReBAR support.

I’m aware than @Kuri0 in his Resizable BAR DXE driver claims to also force 8 GiB BAR on 5600XT as a special case:

…but I don’t know whenever this was tested under Windows.

So, in resume: Can this issue on Radeons 5600XT be fixed VBIOS side by making it announce up to 8 GiB ReBAR like the 5700XT does?


Edit by Fernando: Thread title shortened

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What is your system anyways?

Have you tried to contact official support from msi? tried other vbioses?

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Core i5 12600K
MSI PRO Z690-A WIFI DDR4
I’m testing with both MSI BIOSes (Currently sticking to 1.70) and Dasharo (Coreboot + edk2/Tianocore). Actually, I was intending to ask for the 5600XT special case fix to be implemented directly there.

The VBIOS matches this one: VGA Bios Collection: MSI RX 5600 XT 6 GB | TechPowerUp
Which is the latest available. Older VBIOS should clock the RAM lower (For those unaware, 5600XTs nominal clock speeds were increased post launch via VBIOS updates), so it is a downgrade.

No, didn’t asked MSI. Don’t seem to be worth the time, otherwise this should have been likely fixed since this is not an unreported issue. AMD was contacted by another guy but they never replied: AMD Smart Access Memory not enabling in BIOS according to GPU-Z | Page 4 | TechPowerUp Forums

1 Like
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Maybe try to ask msi support and persuade them if you could, same thing happened in asus z68/p67 mobo i forgor in this forum but he asked to fix the uefi stuff and asus give a revised bios for him, and he could fully boot to uefi (before it cant just blackscreen)

Have you tried to crossflash other vbioses from sapphire or xfx or his? the one that supports 8gb of rebar? since your board is rebar capable so no rebar mod needed. its the vbios itself… so yeah hoping msi did support to the card and give u a fixed vbios would be good.

Msi did provide latest vbios update through msi center right?

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@zir_blazer i don’t think anyone here knows how to modify the VBIOS to fix this if MSI isn’t going to release an update for it. it affects other 5600 xt cards too

i think you’re options are either using ReBarUEFI driver instead of built in or asking MSI support to make a BIOS for your motherboard which overrides the supported sizes for your GPU.

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Look at the message [Guide] How to Modify a Polaris (Radeon RX Series) GPU - #162 by bigguygeo

PCI CONFIG section maybe setting this?

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Hi! Thanks, already finished two vbioses for wx4150, wx4170 and some more. With Linux source it was easier to do. Pcie config with ShiftLeftBit

BTW. Do you know, does anyone was able to wide modify vbioses of RX5xxx, RX6xxxx ?

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Not sure about new cards, check RBR Team or igorslab

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How similar 5600 bios is to polaris? Check the polaris docs, on page 50 it is written exactly where the ROM straps are, 0x70-0xF4

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RED BIOS Editor (by IgorsLab) is able to set Sub Vendor / Sub ID on Navi so it is possible to edit the PCI configuration of it. But there aren’t any open source tools which can do it so no idea how.

The bits for used in the BAR configuration probably same as Polaris though so could search for bytes configured how it is (1GB BAR).

The checksum will have to be recalculated also but that’s probably the easiest part.

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Just created an account to revive this thread: has anyone succeeded with Radeon 5600xt and Resizable BAR?

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About half a year ago, someone that was in contact with a dev of the Red BIOS Editor contacted me and provided me with modded VBIOSes to test:

testing-rebar_2card8gb
testing-rebar_2card8gb1920×1080 494 KB

This was supposed to eventually be usable with RBE to mod 5600XTs VBIOS but not sure if anything happened with it.

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Mine is 6Gb, so those VBIOSes won’t do for me. Even if it was an 8Gb I wouldn’t dare to try it, I was looking for something a little more tested… I’m from a 3rd world country and buying this GPU took me years, can’t afford to brick it.
Thanks anyway, no RBAR for me then…

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All 5600XTs are 6 GiB, unless you missed GPU-Z.
ReBAR works with power of two sizes, so 4 GiB is not enough, you have to jump to 8.

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You discovered how ignorant I am in the matter. Well if you still have those VBIOSes around I might some day gain the courage to test 'em

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If you are still interesed for mods, go here: Radeon RDNA1 Series VBIOS Configuration