AMD Radeon RX 7900 XTX + RX 7900 XT Linux Support & Performance
While there is upstream, mainlined RDNA3 graphics driver support in time for the Radeon RX 7900 series launch day, the initial experience of enjoying these graphics cards was a bit problematic. In preparing for this launch day testing while waiting for the graphics cards to arrive, I completed my re-testing of my prior AMD Radeon / NVIDIA GeForce graphics cards with the latest Linux drivers as usual... For this testing the plan was to use an AMD Ryzen 9 7950X system with ASUS X670E HERO motherboard, 2 x 16GB DDR5-6000 memory, and WD_BLACK SN850 NVMe SSD.
Testing of the prior AMD and NVIDIA graphics cards on this modern Zen 4 system went great... The Radeon RX 6000 series and prior were running wonderfully on the very latest open-source driver stack. But then I went to install the Radeon RX 7900 XT and RX 7900 XTX graphics cards once they arrived... Sure enough, the open-source drivers were working! It was great to see even with Linux 6.0 the RX 7900 series were running... And that the RADV Vulkan driver was also firing up for various games -- both Linux-native Vulkan games as well as some Windows games running on Linux by way of Valve's Steam Play with Proton and DXVK / VKD3D-Proton. RADV is primarily developed by engineers from Valve, Red Hat, and other parties external to AMD. But they've been working on GFX11/RDNA3 changes in advance based in part on looking at the changes made by AMD engineers to the LLVM AMDGPU shader compiler back-end, the RadeonSI Gallium3D driver, etc. They may also have some early hardware access from AMD but no official confirmation or details to share publicly in this article. In any event, it was nice seeing even RADV working on these graphics cards for launch day.
But from this Ryzen 9 7950X system when it came to running benchmarks, the performance was coming up very short... Around half the performance that would be expected or so. No matter the Linux kernel version and other components on the Zen 4 system the performance was coming up well short of expectations. After days of troubleshooting, I decided to fallback to using an older Zen 3 system. Surprisingly, as soon as installing the Radeon RX 7900 series graphics cards onto a Ryzen 9 5950X system while using the same software stack as with the Zen 4 system, these RDNA3 graphics cards were roaring! With the Zen 3 system the Radeon RX 7900 series were immediately delivering great performance and much better than the Zen 4 system.
AMD is still looking into this issue but current thinking is it may be an AMDGPU firmware issue that will be addressed in a forthcoming firmware release and/or it may be an issue around the DDR5 EXPO memory configuration or other related platform issue, which should be addressed by a system BIOS update. In any event after spending days troubleshooting the Zen 4 system, for today's launch day testing I resorted to the Ryzen 9 5950X system for delivering these benchmarks. Stay tuned for a follow-up article once getting the Ryzen 9 7950X system sorted out and to see the benchmarks there. Thus I was also scrambling at the last minute to re-test the older graphics cards on the 5950X system given this issue.
In any event when running the Ryzen 9 7900 series graphics cards on the older Zen 3 systems as well as brief testing from an Intel Raptor Lake system, there were no performance problems encountered like there was with this Zen 4 system.
(Launch day morning update: It looks like it may be related to the AMD EXPO mode with Zen 4... AMD is aware of some system configurations where the EXPO feature will set the BIOS SoC power out-of-spec that can lead to PCIe device issues. Forcing it to 1.25V for the SoC power via the BIOS is the workaround. With my ASUS configuration the SoC power was being set to 1.252V and some tentative tests at 1.250V for the SoC power are looking like the performance issues go away... Again, just an issue I've seen with the RX 7900 series and not other graphics cards but in any case will hopefully be better handled by a BIOS update.)