BIOS Feature Request: Add ability to specify UMA size on AMD APUs

Some values persist, some values reset on boot, some reset on failure. Changing some values also causes the bios to change other values.

There’s an initialization vector that reset much of the CBS values to defaults too, although it must either be loading the bios stored values from elsewhere or it knows to skip it.

I’ve tried altering just about everything that seems like it would adjust vram size with no luck. It’s likely the bios code itself needs to be patched since it keeps resetting UMA_SPECIFIED to UMA_AUTO on boot. I don’t know where auto and game optimized pull their ram settings from either, although I believe I’ve had a few boots where auto booted with 4GB vram instead of 512MB. I’m not exploring this too methodically yet though, I was hoping for an easy win.

I did notice some variables in the ConIn section as well as a vga section are changing as I’m messing with settings, so I may possibly have some other settings to explore. I’m not too worried since the bios seems to reset to factory defaults if it’s the unable to boot.

This tool might be helpful: [TOOL] SREP (SmokelessRuntimeEFIPatcher) - BIOS Modding Guides and Problems - Win-Raid Forum

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Having got comfyui working today, I’d like to get it out of lowvram mode. I have 96gb installed and can only use 4gb of it in stable diffusion.

I’d really like to see us be able to carve out at least 16gb until PyTorch gets sorted to use gtt.


This would be great. I can volunteer for some testing. I have been looking for away to do this myself with no luck.

@Kieran_Levin , is there a chance this will be raised with Insyde and/or AMD? Even keeping it a hidden option accessible through Smokeless would work…

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This would be huge as I really don’t want to go back to windows at all to do any machine learning.

Also one of the reason I bought a lot of RAM.

I don’t think we have a way to vote with our wallet for this feature request (like a feature bounty) but I would definitely put some money towards this if it meant we could get it sooner rather than later.

Hopefully we get some more info from someone on the FW team.

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If you want to invest time, money and or dev-work then that would be far more effective in developing the software to work with dynamic host memory allocation instead of waiting for others to support the legacy workaround in firmware.

There has even been some movement for example in pytorch of developers realizing that this would be the cheapest way to get very memory intensive models to run and going over why the plugin-hack does not work and what needs to change to get the host-allocation to work for everything.

Also the way how you’d get non-power-of-2 memory sizes usable for the iGPU and potentially more than half of the system memory.

While I agree this is the better long term solution, it is not the most practical right now.

By fixing this one issue several dozen pieces of software would just work, no more work needed. If we focused efforts on all the different libraries and apps we want we would need to fix a couple dozen before we put a dent on perception on how useful fixing this is.

I am also guessing that most people who have this issue just go back to windows whenever they want to do some testing or experiment (or playing the games they cant with this).

On the game front it might not be noticeable because most legacy games (where this can’t be patched) do not use > 4Gb or vRAM.

I started looking at some of the info with efivar, I think that some of the changes are overwritten by the bios because it reloads the settings from its -db setting, so in order for changes to stick changes might need to be done on the variable and the -db setting too?

Just wanted to chime in and say I also want this feature, a few things I’ve used that were lazily ported and designed just for dGPUs will crash if they encounter too little VRAM. To the people saying this is a “hack” and not a best practice, welcome to firmware workarounds, that’s more or less what they all are, haha. Back in the BIOS days there were all sorts of flags to let a handful of programs or a single OS work right on a board, and there’s still all kinds of legacy cruft that can be enabled in most BIOS as workarounds for people with very specific needs from their workflows. This feature would be useful to some of us, and its existence would have no impact whatsoever on everyone else who only does things the “right” way.

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I still think having a shim program that dynamically requests the ram and then launches the problematic thing with that is better than just statically walling of a ton of ram for them.

But something like that would definitely help a lot even if it is a hack.

While I understand the other system would be better and more flexible in many cases, having something in the firmware means never having to worry if in five years someone will have updated this hypothetical program to work with the latest OSes. Furthermore it makes sure it actually works on more OSes than just whatever the current version of Windows is, which in my experience is usually what ends up happening with useful tools like that. Since this is a problem with the way the software interfaces with the hardware itself, it’s good to have a fallback solution as close to the metal as possible. A hypothetical shim program would be great, nothing is stopping anyone from developing that, but this thread is about wanting a UEFI based option, specifically.


I just want to mention that I tried this on Lenovo ThinkPad T14s (Ryzen7 PRO 7840U, 32 GB RAM), and their BIOS does actually provide this configuration. They have an automatic mode, just like Framework, but they also have configurable manual modes that allocate 1 GB, 2 GB, 4 GB, or 8 GB of memory. I am not sure if 64 GB RAM enables even more options in the BIOS. So it should be possible to implement this feature.


Not on the 64 GB P14s I played with back in September. 8 GB was still the largest option available.