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 was the Achilles heel of ATI's SB400 series south bridge chips, and although the SB600 is certainly an improvement, it's consistently slower than the nForce 590 SLI. These aren't trivial margins, either, particularly when both implementations offer identical CPU utilization.

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

CPU utilization is a little lower on the 590 SLI, but not by enough to get worked up about.

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

Early ATI south bridge chips had serious PCI performance issues, which is why we started testing PCI throughput in the first place. It's a good thing we've kept testing, because the 790F's PCI Ethernet throughput is a good 75Mbps off the pace set by the 590 SLI. Sure, AMD's CPU utilization is lower, but it's pushing fewer bits.