ASUS uses its menu based Award BIOS setup. We updated our board to version 0121 which was the latest at time of release. This BIOS enhanced some of our overclocking features that failed when running original supplied BIOS, 290MHz FSB clocks would result in random reboots but with the new BIOS we managed to get higher clock speeds.
ASUS has changed the layout of the board somewhat, normally we go to the advanced menu, this time it's under the Extreme or Extreme Tweaker menu which is where all the overclocking settings are located that you will need. To gain access to the overclocking submenus you need to first set the AI Tuning feature to manual.
First we look at the overclocking features under the Overclocking Sub-menu. First is the CPU Frequency. This controls the FSB of the CPU clock; you can adjust it from 200MHz to 400MHz in 1MHz increments.
Next is the CPU Multiplier. This allows you to change your Athlon 64's CPU ratio, you can go as low as 4x up to the maximum your CPU supports, in our case its 10x. If you have a FX series, you can go as high as the board supports, which we aren't sure of.
Next is the memory clock frequency, you can select DDR2-400, DDR2-533, DDR2-667 and DDR2-800. Next are the PCI Express frequency controls for the PCI-E x16 slots, you can go from 100MHz up to 150MHz in 1MHz increments. Lastly you have the ability to control the Hyper Transport dividers and speeds; these are self explanatory to any AMD user.
Now we go back to the Extreme menu and go to the overvoltage menu. This controls all of the voltage options for the board. First off is the CPU Voltage Range, rather than going though separate voltages you have a range to select from. Once you select a range you can then edit the voltage in 0.01v increments in that range, you can basically go from 0.85v to a max of 1.85v in 0.01v increments with this setup, a much better setup than any other board manufacturer has.
Next comes DDR-2 voltage. ASUS has the best range by far of any board here, 1.8v standard up to 3.45v in 0.05v increments. HT Link and NB Core voltage go from 1.2v to 1.5v in 0.05v increments. HT link voltage is for the CPU to Northbridge voltage and the NB Core is for the Northbridge voltage. SB Core and SB PLL voltage runs fro, 1.5v to 1.8v in 0.05v increments, SB Core controls the Southbridge chipset voltage, SB PLL controls the clock generator for the Southbridge.
With all these features we managed to get our FSB up to a maximum speed of 361MHz with a CPU voltage of 1.45v, DDR2 voltage at 2.2v, NB voltage at 1.3v, SB Voltage at 1.55v and DRAM at 1:1 - this yielded us a CPU clock speed of 2.16GHz (361MHz FSB x 6).
For your reference, we are comparing the ASUS Crosshair against the DFI NF590 SLI-M2R/G Lanparty motherboard which managed a higher FSB of 375MHz FSB - it's certainly one of the best new Socket AM2 motherboards on the market right now, so it will be interesting to see how ASUS compares against DFI.