POST shows vital statistics, including RAM settings

A fair selection of BIOS settings include vDIMM, vCore, and chipset voltage

BIOS supports up to 400MHz bus in 1MHz increments

A wide range of DRAM ratios are provided

The A64 bus clock of 200MHz (before HT multiplier) can be raised as high as 400MHz by scrolling to the chosen setting. Both the CPU core voltage range of 0.900v to 1.700v and chipset voltage of 1.5v to 1.70v are reasonable, but a DIMM voltage range of 2.6-2.9v seems a bit restrictive. Memory ratios go from 1/2 bus to 5/4 bus, but are likely dependant on the CPU core revision used. While the 216MHz setting appeared ineffective, the 233MHz and 250MHz settings worked on our Venice core. Both were reported incorrectly below stock speed and differently by nTune viewer and CPU-Z, but Sandra memory benchmark showed a slight gain in bandwidth.

To find the highest bus speed regardless of the capabilities of our CPU and RAM, we set the CPU at 6x bus and RAM at 2/3 bus (133MHz, DDR266). Using the included version of nTune, 220MHz at 5x HT and 250MHz at 4x HT seemed to be the limits of overclocking, regardless of other settings.

How could other settings, such as chipset voltage, have no affect on the clock ceiling? It appears to be an issue with this nTune release. We tried a newer version of nTune, only to find it maxing out at 246MHz using the 4x HT multiplier. It was decreasing memory timings and increasing the performance of other busses first. That left us doing things the old fashioned way, in BIOS.

The VNF4 Ultra tested stable at 309MHz FSB using BIOS overclocking

We ran our full benchmark suite against the overclocked system and found our highest stable bus speed at an amazing 309MHz. But there's bad news for those of you accustomed to simply dropping the bus speed following an unstable setting; that doesn't work with this motherboard. It didn't matter whether we used nTune, ClockGen, or BIOS menus: Any instability detected by the board will reset nearly everything, not just the bus speed. Worse, the system has to boot successfully beyond POST before it will allow anything above stock settings to be saved.

The process gets rather old quickly: Boot the system past the POST screen after defaults are restored, reboot, go back into BIOS, change the HT multiplier under one menu, disable "Cool and Quiet" under another, disable smart fan controls in still another, set Frequency/Voltage control to "manual", reboot, and finally set your overclock. Any failure to follow the whole routine will likely cause the BIOS to restore defaults again. Some people have complained they couldn't get their settings to stick with this board -- we believe it's because automatic BIOS reset is on a hair trigger!