AMDGPU vs. Radeon DRM With Linux 4.14 On GCN 1.0/SI GPUs

It's been a while since last testing the older GCN 1.0 "Southern Islands" graphics cards with the AMDGPU DRM driver rather than the default Radeon DRM driver. Here are some fresh comparison tests using some original GCN graphics cards with the two DRM drivers while pairing it with Mesa 17.4-dev, including Vulkan tests that are made possible by switching over to the AMDGPU Direct Rendering Manager driver.

GCN 1.0 Sothern Islands and GCN 1.1 Sea Islands graphics cards continue to default to using the mature Radeon DRM driver rather than AMDGPU DRM, which is treated as experimental for GCN 1.0/1.1 while being the requirement for GCN 1.2 graphics processors and newer. Through Linux 4.15 at least, GCN 1.0/1.1 GPUs will still be using the Radeon DRM by default, but the AMDGPU support for these older generations of Radeon GPUs is becoming more mature with less regressions, no display headaches this time around, some UVD porting for GCN 1.0 on AMDGPU being a work-in-progress, and PowerPlay fixes having recently landed in the kernel.

For this testing I used a Radeon HD 7950, R9 270X, and R7 370 while testing both Radeon and AMDGPU using the Linux 4.14 kernel paired with Mesa 17.4.-dev built against LLVM 6.0 SVN via the Padoka PPA. When using the AMDGPU kernel driver there is also GCN 1.0 support in the RADV Vulkan driver, which doesn't support the Radeon kernel driver, as one of the advantages of using this newer DRM driver. With newer kernel releases, switching to the AMDGPU DRM driver is as easy as booting with amdgpu.si_support=1 radeon.si_support=0 (or amdgpu.cik_support=1 radeon.cik_support=0 for GCN 1.1 graphics cards).

Overall the GCN 1.0 experience with AMDGPU on Linux 4.14 was very good. The only problem to report was the RADV Vulkan driver failing to work with Dawn of War III on the tested graphics cards while the OpenGL renderer worked fine and the other Vulkan Linux games had run fine.

Via the Phoronix Test Suite are various AMDGPU vs. Radeon OpenGL results followed by the Vulkan vs. OpenGL performance on these three GCN 1.0 graphics cards.