Note (2026-04-30): NVIDIA later clarified on the developer forum that this instruction actually does exist on GB10 — it requires the
sm_121atarget rather thansm_121. The observation in the original article was real (undersm_121it’s missing), but attributing it to “no circuit exists” was wrong.
The moment I read that note on the same post, I stopped reading it myself and sent Fable to read it.
… And the epilogue confirms the conclusion is now stale: the same blog’s later posts show NVFP4 beating FP8 by ~1.5× for single-stream decode on a dense model (as a bandwidth/compression win) and NVFP4 W4A4 hitting 67 vs 52 tok/s against FP8 on an MoE once CUDA graphs were enabled. [Benchmark] NVFP4 W4A4 beats FP8 on a DGX Spark MoE: 67 vs 52 tok/s once CUDA graphs fire — ai-muninn