Tensor core throughput is scaling much faster than the rest of the GPU, creating an unexpected bottleneck for transformer attention. On NVIDIA Blackwell B200 chips, bfloat16 tensor core throughput jumped from one to two point two five petaflops compared to Hopper, yet shared memory bandwidth and special function unit capacity remained completely flat.
Because of this hardware asymmetry, matrix multiplication is no longer the primary limiter in modern attention kernels. Instead, forward passes stall on the transcendental operations in softmax exponential calculations, while backward passes bottleneck on shared memory traffic. FlashAttention-4 tackles this discrepancy through an algorithm and kernel pipelining co-design that explicitly overlaps matrix math with these hardware resource constraints.
Hardware scaling has broken traditional kernel assumptions, and pipeline scheduling across asymmetric execution units is now where real speedups happen.






