http://www.anandtech.com/showdoc.html?i=1752&p=2
Today AMD announced the name of their ClawHammer processor - Athlon XP 64. At the same keynote they had nForce2 motherboards running with a 400MHz FSB. We just received confirmation (although AMD won't announce it until much later) that Barton will be shipping with a 400MHz FSB and the performance boost from the new FSB is pretty healthy. On current processors the use of a 400MHz FSB will improve performance anywhere from 0 - 15% on the nForce2 platform, obviously depending on the benchmark.