ASRock uses the Award Tab BIOS as we like to call it. This BIOS is used by Intel on their reference boards as well as ASUS on all of their current boards, which makes it pretty familiar. But it is a bit daunting at times as there are quite a few different menus for you to go through to find all the overclocking settings.
Under the Advanced tab you will find a plethora of sub menus. Under the Chipset Features menu you'll find all the overclocking relevant settings which are also under some sub menus.
Base Clock (MHz): 133MHz to 300MHz in 1MHz increments
PCIe Frequency (MHz): 100MHz to 200MHz in 1MHz Increments
CPU Voltage: 0.84375v to 1.6v to 0.00625v Increments
DRAM Voltage: 1.53v to 2.451v in various Increments
DRAM CRTL Ref Voltage: -0.06741v to +0.08v in various Increments
DRAM DATA Ref Voltage: -0.06741v to +0.08v in various Increments
IOH Voltage: 1.11v to 1.49v in various Increments
VTT Offset Voltage: +0mV to +300mV in 100mV Increments
ICH Voltage; 1.12v to 1.56v in 0.02v Increments
IOH CSI Voltage: 1.12v to 1.56v in 0.02v Increments
IOH/ICH PCIE Voltage: 1.52v to 1.9v in 0.02v Increments
CPU PLL Voltage: 1.82v to 2.50v in 0.02v Increments
Now this was impressive! - For a board that we wouldn't put into the tier 1 category, it has managed to give us a very impressive overclock of 185MHz BCLK, but it was the fact that we managed to hit 3.7GHz on the CPU (100% stable) which really gave us a good notion about the board.
Important Editor Note: Our maximum overclocking result is the best result we managed in our limited time of testing the motherboard. Due to time constraints we weren't able to tweak the motherboard to the absolute maximum and find the highest possible FSB, as this could take days to find properly. We do however spend at least a few hours overclocking every motherboard to try and find the highest possible overclock in that time frame. You may or may not be able to overclock higher if you spend more time tweaking, or as new BIOS updates are released. "Burn-in" time might also come into play if you believe in that.