BIOS Options

Our Asus M3A78-T has been flashed to the latest BIOS for additional CPU support as well as to have the best chance of a successful overclock.

To get started, enter the motherboard’s BIOS (typically by hitting the delete key at the POST screen). Be sure to check your motherboard manual and know how to clear the CMOS (usually a jumper) should a change prevent the system from POSTing. Keep in mind, if this does happen, any changes previously made such as time/date, disabling integrated graphics, boot order, and so on, will be lost.  If you are new to exploring the BIOS, pay special attention to any changes you make, and record your initial settings if you are leery of remembering all of them.

Merely navigating within the BIOS is completely safe, so if you're new to under-the-hood tweaking, feel free to poke around. But be sure to discard any accidental changes or exit the BIOS without saving if you fear you may have unintentionally altered a setting. This is typically done with the Esc key or an exit menu option:

Let’s dig into our Asus M3A78-T BIOS with some illustrations. BIOS menus will vary between motherboard manufacturers, so you may need to consult your manual to find these options in your BIOS. Also keep in mind that the options available will vary significantly between motherboard models and chipsets. 

The Main Menu is where you set the date and time, as well as access information on the connected drives. Menu options with the blue arrow head can be expanded. System Information, for example, shows the BIOS version and date, processor brand, the current rated speed, and the amount of system memory installed: 

The Advanced menu is a collapsed set of sub menus. The CPU Configuration menu gives processor information and also contains some of the options we want to disable while trying to find our maximum overclock:

Most of our time will be spent in the Jumper-Free configuration menu. Gaining access to the important options is done by setting AI Overclocking to manual. With a different motherboard, these options will likely be found in a different menu:

We now have access to the multipliers that will need adjusting. Notice that in this BIOS, the CPU multiplier steps in half-increments and the northbridge multiplier is in full increments. But the HT-link speed is set directly in MHz and not as a multiplier. These options will vary greatly between motherboards and for some, you may be setting FID and DID as discussed earlier:

Under DRAM Timing Configuration, we can easily set the frequency of the memory, whether it is DDR2-400, DDR2-533, DDR2-667, DDR2-800, or DDR2-1066 as shown here. There is no need to set memory multiplier or divider ratios in this BIOS. Under the DRAM Timing Mode, the current memory timing can be set manually or automatically. Tightening timings by lowering the number can increase performance. Unless you have already fully-tested and known stable RAM timings at various memory speeds, when overclocking, it’s a good idea to manually set the CL, tRDC, tRP, tRAS, tRC, and CR timing to a relaxed (higher) number. Also, higher frequencies may be possible by setting the tRFCs all to a higher number such as 127.5 or 135. 

Later, many of these can be tightened back up while tweaking for more performance. This procedure of tightening one memory timing at a time is very time consuming, but is a worthy investment for maximum performance and stability. When running your system memory out of spec, be sure to stability test it with a utility such as a Memtest86 boot CD, since memory instability can cause harmful data corruption. With that being said, it is also quite possible to allow the motherboard to adjust these timings automatically (which is usually relaxed) and just proceed with your overclocking.