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 VelociRaptor.

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

From the SB600 through the most recent SB750, AMD's south bridge chips have all used essentially the same storage component. The SATA controller is a Silicon Image design, and from the beginning, it's had inconsistent performance in AHCI mode, a mode that enables access to some key SATA features like Native Command Queuing and hot-swapping. The SB750 will soon be replaced, but we thought it appropriate to explore the AHCI issue one more time to see what's what with the latest drivers.

Below you'll find results for the 790FX running in IDE mode with AMD's Catalyst 9.5 IDE drivers. We've also tested the AMD chipset in AHCI mode using the generic Microsoft AHCI driver that Vista automatically installs. AMD has its own AHCI drivers, too, and we've tested their latest 3.1.1540.127 revision.

When paired with Vista's AHCI driver, the 790FX manages to keep up with the nForce 980a SLI. Running the AMD chipset in IDE mode results in significantly lower transaction rates, likely due to this mode's lack of support for NCQ. What's even more interesting is the performance of AMD's own ACHI driver. It's no quicker than IDE mode up to 32 outstanding I/O requests, and after that, it's actually slower.

In the past, we've only seen decent AHCI performance from AMD south bridge chips combined with unreasonably high CPU utilization. That isn't the case here, though. The Vista AHCI driver does consume more CPU cycles than the nForce, but we're only talking about a couple of percentage points.

Today's lesson: AMD's AHCI drivers are still broken. Horribly, horribly broken.

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

The 790FX is back in IDE mode for HD Tach, and that may be why it stumbles in the sustained write speed test. However, we've seen inconsistent performance from the SB750 in the write speed test before, particularly when running in AHCI mode with Vista's drivers.

There's no difference in random access times between the 790FX and 980a.

Although overall CPU utilization is high in HD Tach, the AMD and Nvidia chipsets are evenly matched.