The difficulty with how most GPUs are connected to the rest of the system is that the data has to go RAM -> CPU -> GPU. If it could go directly RAM -> GPU, then

The difficulty with how most GPUs are connected to the rest of the system is that the data has to go RAM -> CPU -> GPU. If it could go directly RAM -> GPU, then the calculations would be better, but still not great as PCIe is still lower bandwidth and higher latency than RAM -> CPU. It's not about GPU performance, it's about the latency and bandwidth of getting that dat to the GPU. If once you ship data to the GPU, you reuse it many times for many calculations, that cost is amortized and it doesn't matter as much. But if you ship data to the GPU and use it once, then that cost will probably not be amortized. I think of databases tending to fit in the latter category.