BIOS and Overclocking
The Asus P5NSLI is equipped with a Phoenix/Award BIOS that is is relatively complete and easy to navigate. From within the BIOS users have the ability to configure, enable or disable all of the board's integrated peripherals, and monitor voltages and clock speeds. The P5NSLI also has a complete set of memory timing options that offer good flexibility for fine tuning memory performance. Memory voltage options, however, leave a little to be desired.
The P5NSLI's standard BIOS menu screens don't reveal anything out of the ordinary, but they will give you a "feel" for the general layout and organization of the options. Each individual screen has a host of menus that tunnel deeper and deeper as the options get more complex. Overall, it is very similar to the BIOS derivatives used on most other motherboards, but navigating through Asus' BIOS menus does take some getting used to if you've never experienced them before.
Because this board isn't targeted strictly at hardcore overclockers and enthusiasts, Asus didn't go over to top with the P5NSLI's overclocking options. That's not to say the P5NSLI can't be used for some mild overclocking, however -- it does have a fair amount tweaking tools and Asus also gives users the ability to save overclocked settings in the "O.C. Profile" menu. There just aren't any overly aggressive voltage options available on the P5NSLI, especially for memory tuning.
The Asus P5NSLI gives users the ability to raise the FSB speed from 100MHz to 400MHz in 1MHz increments (quad-pumped to 400MHz - 1600MHz) and the PCIe clock can be cranked up to 150MHz, also in 1MHz increments. And the memory clock can be dialed in manually as well. The CPU multiplier can be manipulated when using an "Extreme" processor, but not when using standard Core 2 CPUs. The CPU voltage can be raised as high as 1.6v with fine granularity, and the chipset core and CPU termination voltages can be set as high as 1.5v or 1.35v, respectively. There are a good assortment of memory timing options available, but the memory voltage maxes out at a paltry 2.1v. 2.1v is a very low voltage considering many high-end memory kits actually require 2.2v to function reliably at their rated timings. This is a very important point to consider when shopping for memory to be used on this board.
To evaluate the Asus P5NSLI's overclocking ability, we first bumped up the CPU and memory voltages up to 1.4v and 2.1v respectively, and gave all of the other peripherals a .1v bump as well where applicable. Then we dropped our CPU's multiplier to 10x and raised the FSB frequency until the test system was no longer stable. In the end, we hit a maximum stable FSB of only 323MHz. The P5NSLI actually booted with higher FSB frequencies, but we couldn't stabilize Windows until we dropped things back down to 323MHz. Because we could not hit any excessively high FSB speeds, we were actually able to bump our CPU's multiplier back up to its default setting of 11, for a final clock speed of about 3.5GHz. Perhaps with higher memory voltage options and some BIOS tuning, Asus can improve the overclockability of the P5NSLI, but considering this is a mainstream motherboard we aren't expecting any miracles.