[Beowulf] Disappointing floating point performance for X5560 versus SPECmarks?

[Mark Hahn]

> However, our own benchmarking using nbench, unixbench, and a home-grown
> utility (twobod) all show that any differences are attributed to clock speed.

do you have any sense for whether these are entirely in-cache benchmarks?
that's the most obvious explanation.  nehalem is all about the new memory
interface - the cores are basically just core2's (with HT added and some 
smallish tweaks to caches, etc).  basically 2x 2-wide GP flops/cycle/core.