[tptacek]

Salted SHAx passwords are basically the entire reason GPU John The Ripper and oclHashcat exist, although SHA2-512 is significantly slower than SHA2-256, so if you're going to use a terrible SHA-based password hash, SHA2-512 is your best bet.

[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.