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.

AMD's south bridge chips have never offered the best USB performance, and the SB750 is no exception. The nForce easily outguns the 790GX here.

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

Although the 750a and 790GX offer equivalent throughput here, the AMD chipset's CPU utilization is a little higher.

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

Yeah, we couldn't get our VIA Velocity-based Gigabit Ethernet card working in the Gigabyte 790GX board. The card was detected in both slots, but Vista refused to install not only its own embedded drivers for the card, but the latest standalone driver package, as well. This is likely a compatibility quirk associated with the motherboard and early BIOS revisions rather than a problem with the 790GX chipset.