A GPU that shipped in 2012 is finally getting proper Linux support thanks to Timur Kristóf, an engineer on Valve's Linux graphics driver team. The Radeon HD 7870 XT, a cut-down variant of AMD's Tahiti silicon, has never once worked correctly with open-source Linux graphics drivers. A patch series posted to the amd-gfx mailing list resolves the issue by fixing how the AMDGPU kernel driver handles GPUs with partially disabled TCC cache blocks.
The root cause is unusual. HD 7870 XT cards were "harvested" from higher-end Tahiti dies, with defective or excess cache partitions fused off to meet the lower-tier spec. The AMDGPU driver never accounted for this kind of partially disabled TCC configuration, meaning it would fail outright on these GPUs rather than working around the missing cache blocks. A Freedesktop bug report documenting the problem dates all the way back to 2013, with another report surfacing in 2023 confirming the card still did not function under Linux at all.
This fix is part of Kristóf's broader effort to make the modern AMDGPU driver the default for older GCN-era hardware. His earlier work brought AMDGPU improvements to GCN 1.0 and 1.1 cards, replacing the legacy Radeon kernel driver and unlocking RADV Vulkan support for Southern Islands and Sea Islands GPUs. More recently, he landed AMDGPU fixes for Kaveri and other GCN 1.1 APUs targeting Linux 7.1. The HD 7870 XT patches represent another step in ensuring that even the most obscure GCN 1.0 hardware configurations work properly with the modern driver stack.
