What about using both SMP and GPUs?

GPUs can also be used to process a separate FAH assignment while running SMP (see the GPU FAQs) but some CPU processing is required to support that GPU. If you also process with a GPU from AMD, that GPU support function consumes one CPU core and less is available for SMP processing. You can expect to higher SMP performance by dedicating fewer CPU-cores to SMP to avoid resource conflicts. NVIDIA GPUs do not currently require a full CPU’s resources.