Class 3 UEFI and GPUs \ VOGONS

Class 3 UEFI and GPUs

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First post, by pappyN4

Posted on 2025-03-17, 19:52

pappyN4 Offline

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Joined: 2014-10-16, 00:41

It looks like AMD has announced that RDNA4 (RX 9000 series) will need Class 3 UEFI to work.

Intel already enforced Class 3 starting with their 11th gen iGPUs.

Does anyone know what generation of NVIDIA GPUs forces class 3 or does it still work with class 2 (UEFI with CSM enabled)? I cant seem to find anything concrete online.

Related question. Would a class 3 card work if you were able to boot into windows with a different card?

So for example, motherboard has UEFI/w CSM enabled. A GT700 series in the second GPU slot set as primary boot in the motherboard and boots into windows. Would the class 3 GPU in the primary slot be visible, able to install drivers for it, disable the second card in windows, and the next time you reboot the computer will POST using the secondary card and then switch to primary once it boots into windows?

Something along the lines of a dual boot situation where the second card would already be used for an older version of windows, but use a newer primary card with modern windows.

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Reply 1 of 3, by Azarien

Posted on 2025-03-17, 22:23

Azarien Offline

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It is important for your PC to be configured for UEFI Mode [by this they mean CSM is disabled] to ensure optimal compatibility, performance, and user experience with your AMD Radeon™ RX 9000 Series and newer graphics cards.

To fully leverage the benefits of UEFI, only UEFI Mode will be officially supported

[in CSM mode] compatibility with older hardware is maximized, but modern hardware like the AMD Radeon™ Graphics may lose access to important and necessary features of your motherboard, such as AMD Smart Access Memory™ technology

I hope that leaving CSM enabled won't be hard-blocked at least for now — just not "officially supported" but still working fine, possibly at the expense of Smart Access Memory, whatever that does.

Reply 2 of 3, by Disruptor

Posted on 2025-03-17, 23:34

Disruptor Offline

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I just have updated my (old) Intel 4770k system to AMD Radeon 9070.
It is true. Now I can see neither the BIOS outputs of my Intel onboard RAID nor the one of my LSI U320 SCSI controller.

Reply 3 of 3, by pappyN4

Posted on 2025-03-18, 00:05

pappyN4 Offline

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Joined: 2014-10-16, 00:41

The Intel iGPU for sure is a hard break. I have a 12th gen Alder Lake N100 mini I was messing with and as soon as CSM is enabled in the BIOS, there is no more video out from the iGPU. It was an old enough issue so I was able to find posts on why it wasnt working.

From this post here the iGPU from Zen4 also looks to have a hard limit.

I figure any dGPU with windows 7 support would work since officially Win7 would need to run under CSM. So that covers up to nvidia 3000 and amd 6000. Unfortunately there's no modern budget cards anymore to buy and test with so left in weird place looking for people with expensive modern cards that would have cared enough to try enabling CSM for fun.

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