Leveling the playing field
Thanks to the Athlon 64's integrated memory controller, most Athlon 64 chipsets perform about the same on the memory-intensive benchmarks traditionally used to evaluate chipsets. However, we did find some measurable performance differences between the Radeon Xpress 200 and the VIA K8T800 Pro recently, and that piqued my curiosity. Turns out that the Radeon Xpress 200 reference motherboard supplied to us by ATI had the HyperTransport clock set at a very curious speed: 200.9MHz. That's nearly 201MHz, and while it may not sound like much, it makes a real difference in CPU clock speeds. Have a look at what CPU-Z shows for the ATI reference board:

ATI's Radeon Xpress 200 reference board

Sneaky, huh? The CPU clock speed is quite a bit higher than stock. What's more, although the HyperTransport speed can be overclocked, there's no way to adjust it down to a true 200MHz on that board.

Funny thing is, the NVIDIA reference board came to us with a 200.9MHz HyperTransport clock, as well.

NVIDIA's nForce4 reference board

NVIDIA's BIOS does offer the option of a true 200MHz HT link (as well as 200.3 and 200.6MHz), but I wanted a fair comparison. The only thing to do was to raise the HT clock on the Asus A8V Deluxe mobo we were using for the VIA K8T800 Pro results to a comparable speed, so that's what I did:

Asus A8V Deluxe with K8T800 Pro

Ok, so it's not exact, but it's as close as I could get.

With the clock speed disparity out of the way, I proceeded to the Athlon 64 memory controller's settings. Using the handy little utility A64 Tweaker and a few BIOS menu options, I was able to match up memory timing parameters almost exactly between the three boards, with the exception of some idle cycle settings on the Asus A8V Deluxe.

ATI's Radeon Xpress 200 reference board

NVIDIA's nForce4 reference board

Asus A8V Deluxe with K8T800 Pro

Tweaked like this, these boards should perform just about identically whenever the CPU or memory controller is the primary bottleneck.