HD Tach
We used HD Tach 3.01's 8MB zone test to measure basic SATA throughput and latency.

The 790i SLI's SATA read speeds are quite competitive, but with our Raptor hard drive, write performance is a little off that of Intel's best. HD Tach's write speed test tends to produce odd results when chipsets that support Native Command Queuing are combined with the WD1500ADFD, though.

Barely a fraction of a millisecond separates random access times...

And CPU utilization is within HD Tach's +/- margin of error for this test.

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.

Although its USB read performance isn't any faster than what you get with Intel's latest chipsets, the 790i's USB writes are slightly quicker. This does come with a slightly higher CPU utilization penalty, although one that's within HD Tach's margin of error.