The Silicon Reckoning settled Vulkan over ROCm. Months later, a smaller question — does the RADV driver's own version matter? — returned +31.6% prefill on identical hardware, from a container, without touching the pinned enterprise host.
Ten models, two families, two drivers, one iGPU. The size sweep meant to map a smooth curve found a cliff instead — dense models fall off it, Mixture-of-Experts models do not. And the newer driver's gift turned out to have a price only dense models pay.
With Ollama disabled and GTT freed, the fleet reran the entire playoff under Vulkan RADV. qwen2.5:14b Q2 dropped from 113 seconds to 21 seconds. No language drift. gemma4:12b Q2 dropped from 93 seconds to 30 seconds. The hardware had been capable the whole time. The backend had not.