VC-Attention: Faster Low-Bit Attention Without Retraining

Nunchux introduces VC-Attention, a training-free low-bit attention method that accelerates video generation by 1.6× on NVIDIA B200 compared to BF16 FlashAttention-4. The technique combines V-Smooth for reducing quantization error and ExpCast-FP8 for eliminating the softmax bottleneck, achieving higher fidelity than existing methods like SageAttention2.