[Gizmo]

Generally speaking, the AMD Athlon and AthlonXP cores perform better when running 1:1. I believe this is due to the way the internal caching is implemented. The upshot is that lower FSB running 1:1 (synchronous) can net you better memory performance than higher FSB running 5:4 (asynchronous) or something like that.

With the Intel P4 family, the caching mechanism works differently, and is less sensitive to memory latency, preferring higher FSB clocks. This is directly opposite the case with the AMD Athlon and AthlonXP cores.

Intels Core family CPUs have continued this trend from what I understand, and thus continue to perform better with high FSB, even at some sacrifice of memory latency. However, with the advent of the AMD Athlon64 and its integrated memory controller, the AMD architecture is no longer so sensitive to memory latency, and thus tends to now also favor higher bus speeds (though in this case it would HT clocks, rather than FSB clocks).

Hope that helps.