[JshWright]

SHA512 is slower on most (all?) current GPUs, but there is plenty of hardware on which it is faster than SHA256.

[tptacek]

Hm. Example?

[JshWright]

It'll (theoretically) be faster on any hardware that supports 64 bit operations, as SHA512 ends up doing fewer block operations.

This assumes you're hashing something at least 8 bytes long, and that your hash implementation is smart enough to use the 64 bit capabilities of your platform.