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.
ATI chipsets have a reputation for dismal USB performance, and the RDX200 doesn't disappoint. Burst and sustained transfer rates are quite poor, certainly not worth the high CPU utilization. To be fair, the Asus A8N32-SLI also exhibits high CPU utilization during USB transfers, but at least its throughput measures up.
Our Firewire transfer speed tests were conducted with the same external enclosure and hard drive as our USB transfer speed tests.
Although it's competitive in most of our Firewire tests, the RDX200's Firewire write speeds lag considerably. The board uses a PCI-based Firewire chip, so we could be seeing the SB450's PCI performance issues popping up again.