Qwen3.8 27B

User reports Qwen3.8 27B at 35.6 t/s decode on an Intel Arc Pro B70 (32 GB) with Vulkan, dropping to 4.5 t/s at 64k context. Setup is llama.cpp b10883 with Q4_K_M and q8_0 KV cache, single GPU, full offload, MTP3 draft (Q8_0, n-max 3, p-min 0.10). Decode collapses ~8x from 1k to 64k on Vulkan while SYCL degrades only ~2.4x (38.5 to 15.8 t/s); prefill falls 562 to 101 t/s on Vulkan. An f16-KV control collapses identically, and MTP gain goes negative at depth on Vulkan. A third-party RX 7900 XTX run holds ~58-60 t/s at 28-30k depth.