USB performance
Our USB transfer speed tests were conducted with a USB 2.0/Firewire external hard drive enclosure connected to a 7200RPM Seagate Barracuda 7200.7 hard drive. We tested with HD Tach 3.01's 8MB zone setting.

USB performance is locked in a dead heat in the burst and read speed tests, but writing starts to spread things out. Interestingly, the X38 system has quicker write speeds than the P35, although both trail the nForce. The X38's CPU utilization is a little higher than can be explained by HD Tach's +/- 2% margin of error in that test, as well.

PCI Express performance
We used ntttcp to test PCI Express Ethernet throughput using a Marvell 88E8052-based PCI Express x1 Gigabit Ethernet card.

Throughput doesn't vary from chipset to chipset. CPU utilization does, and our P35 config shaves 4% off versus the competition. I'll explain why in a moment.

PCI performance
To test PCI performance, we used the same ntttcp test methods and a PCI VIA Velocity GigE NIC.

Our PCI performance testing provides some curious results. Throughput is higher for our Intel-based systems than it is for the nForce 680i SLI. The nForce suffers from higher CPU utilization, as well.