DeepSeek V4.1 Flash 552B (16B active)

User reports DeepSeek V4.1 Flash at 60.8 t/s decode and 2,574 t/s prefill on a 1K prompt using a tuned SGLang build on 4x DGX Spark. Setup is SGLang TP4 with knapcio's recipe, DSpark speculative decoding, Engram tables streamed from NVMe, 262K context, and 100 GbE switch. The model weights are 511 GB and do not fit comfortably on 4 Sparks; memory allocation above 0.92 per Spark crashes. User compares against Patrick Moorhead's results: 62.5 t/s vs ~58 t/s single-request prose, 79.1 t/s vs ~96 t/s single-request code, and 293 t/s vs 494 t/s peak code at 16 vs 32 concurrent requests. User could not reproduce 1M context, 32 slots, or ~0.2 s first token.