OK, it's not that HSA isn't useful, it's that coordination between the CPU and GPU is still stupidly hard and has a lot of CPU-side overhead, making it impractical for small workloads. The problem is that a large number of small workloads still can't be done by a GPU. I'm seriously doubting the limits of "coherent memory access" -- unless the GPU can snoop into the CPU's cache (or the GPU/CPU share L1 cache -- eeek), then you will still need cache flushes and fences. Let's hope that "HSA" is a lot lower overhead than current CPU/GPU combos from AMD/Intel.