Memory Tests
We used SiSoftware Sandra 2007 to measure memory subsystem performance for the Xeon and Opteron test systems. It has the ability to measure combined bandwidth for systems with multiple CPUs able to access memory controllers concurrently. The dual busses to the 5000X MCH in the Gravistar X2 should be tested nicely, with FB-DIMM, while the Opteron's NUMA architecture should see similar increases based on the number of memory controllers in the system.Memory Bandwidth
Xeon remains underfed compared to Opteron, even at higher memory frequencies. A single Opteron on its own can stream data from memory at nearly the rates that two new Xeons can. The FB-DIMM setup and 5000X MCH does offer up nearly 80% more bandwidth than the old shared-bus scheme with Paxville or Nocona, though.
Memory Access Latency
FB-DIMM has the potential to add access latency to a system depending on the memory controller.
Access latency is down compared to the last generation of Xeon, but it can't quite compete with Opteron yet.