Would that be the 667MHz Fully buffered error correcting DIMMs that are required to be used with the 1.33GHz front side bus of the Woodcrest family of processors used in the Apple Mac Pro??? What would you replace them with?
I've read reports that the FB-DIMM architecture forced on everyone by Intel is nothing to write home about. Some speculate that a Core 2 Duo properly implemented might come darn close to a Xeon with the FB-DIMMs.
That's strange... the Intel XEON® 51XX "Woodcrest" family of processors are the Intel Core 2 Duos... and they not only come "close" but are kicking butt against the last generation XEON® processors, the "Dempsey" 50XX line.
In head to head benchmarks, the XEON® 5150, the mid-range 2.66GHz version is 30-45% faster than the fastest "Dempsey", the 3.76GHz 5080. One reason for this is the "Woodcrests" have a 1.33GHz front side bus... while the "Dempsey" has only a 667MHz front side bus.
Intel XEON® "Woodcrest" Benchmarks v. "Dempsey" and AMD Opteron 285