Serial ATA performance
The Serial ATA disk controller is one of the most important components of a modern core logic chipset, so we threw each platform a selection of I/O-intensive storage tests using a Western Digital Raptor WD1500ADFD.

IOMeter
We'll begin our storage tests with IOMeter, which subjects our systems to increasing multi-user loads. Testing was restricted to IOMeter's workstation and database test patterns, since those are more appropriate for desktop systems than the file or web server test patterns.

The 790FX's utterly broken AHCI mode essentially strips the platform of its support for Native Command Queuing—a shortcoming that IOMeter nicely highlights. As soon as we go beyond a single I/O request, the nForce's transaction rate scales much better than that of the 790FX with both the workstation and database test patterns.

IOMeter response times are quicker with the 780a, too.

And quicker disk performance doesn't come with a CPU utilization penalty. Both chipsets are well below 0.5% CPU utilization across all load levels, with the nForce just that little bit more frugal.