ZYFA: Fast and Accurate FP8 Attention on AMD MI355X Zyphra released ZYFA, an open-source FP8 and BF16 prefill attention kernel for AMD Instinct MI355X GPUs, achieving 1.16–1.76× the throughput of AMD's AITER default kernels on activations captured from Mistral-7B, Qwen3-8B and DeepSeek-V2-Lite at 16K tokens and sustained clocks. On Gaussian inputs at 32K tokens, ZYFA's FP8 kernels reach 1.26–1.37× AITER at head dimension 128 and 1.99× at DeepSeek's multi-head latent attention head shape, hitting 53% of the FP8 datasheet peak, while at head dimension 128 their numerical error is 62–78% lower than AITER's FP8 kernel. Zyphra reports that a Hadamard rotation of Q and K halves the full-model FP8 error on Mistral-7B at almost no extra time, and the source code is available at github.com/Zyphra/zyfa. ZYFA: Fast and Accurate FP8 Attention on AMD MI355X Zyphra presents ZYFA Zyphra FlashAttention on AMD - FP8 and BF16 prefill attention kernels for AMD Instinct MI355X https://www.amd.com/en/products/accelerators/instinct/mi350/mi355x.html GPUs. ZYFA is part of the attention engine of our Zyphra Optimization Engine ZOE https://www.zyphra.com/optimization-engine on AMD MI355X GPUs, powering our inference cloud and on-prem deployments. We show that FP8 matrix instructions offer twice the peak throughput of BF16, but attention kernels fall well short of a 2x speedup in practice. On the MI355X at 32K tokens, the FP8 attention kernel of AITER https://github.com/ROCm/aiter AMD’s library of inference kernels reaches 39% of the FP8 peak, while its BF16 kernel reaches 49% of the BF16 peak. FP8 speeds up only the two matrix multiplications of attention, so the softmax between them becomes the bottleneck. ZYFA’s FP8 kernels shrink the softmax, overlap it with the matrix multiplications, and keep the 8-bit probabilities accurate. On attention inputs captured from three models and timed at sustained clock speeds the steady clock under continuous load , they achieve 1.16–1.76× the throughput of AITER’s default kernels Figure 1 , and at head dimension 128 their numerical error is 62–78% lower than that of AITER’s FP8 kernel. This post summarizes our paper, and the source code is available at github.com/Zyphra/zyfa https://github.com/Zyphra/zyfa . Key Results - Speed on real activations: On activations captured from Mistral-7B https://huggingface.co/mistralai/Mistral-7B-v0.3 , Qwen3-8B https://huggingface.co/Qwen/Qwen3-8B , and DeepSeek-V2-Lite https://huggingface.co/deepseek-ai/DeepSeek-V2-Lite at 16K tokens and timed at sustained clocks, ZYFA’s FP8 kernels achieve 1.16–1.76× the throughput of AITER’s default kernels, and ZYFA’s BF16 kernels achieve 1.01–1.02×