Audio performance
Now we'll dive into the south bridges, where the new ICH6 can get more of a workout. We've cut the contenders down to three here, because the 915G and 925X share the same south bridge chips.

RightMark3D measures CPU utilization with a number of audio tasks. We can see how well Intel's High Definition Audio implementation works.

Overall, the 925X does pretty well in these tests, showing CPU utilization generally similar to the 875P's AC97 audio engine. The VIA audio controller on the K8T800 Pro uses much more CPU time, consistent with what we've seen from it in the past. However, there are several mitigating factors here. First, I don't believe RightMark3D tests with any sort of high-definition audio streams that require mixing of high-bit-rate audio data, so it's not really a torture test we're seeing. Second, I'm always wary of CPU utilization tests that report numbers with Hyper-Threading enabled. Generally, software doesn't seem to get a very accurate representation of CPU utilization with HT turned on, because one of the two logical CPUs will be sitting idle. Then again, I'm not sure it's accurate not to have it turned on, either. Just something to keep in mind.

USB performance
We used HD Tach to measure USB transfer rates to a Maxtor DiamondMax D740X hard drive in a USB 2.0 drive enclosure.

The 925X achieves faster read speeds and lower CPU utilization than the 875P chipset. The K8T800 Pro with the Athlon 64 is faster yet, but at the price of much higher CPU utilization. Out of curiosity, I turned off Hyper-Threading and re-ran the test on the 925X. CPU utilization was then reported at 19.4%, still much lower than the K8T800 Pro system.