Overclockers are PC enthusiasts who attempt to increase their system's performance by raising bus speeds and increasing their CPU speed beyond the figure at which it was sold and designed to run. They also quite frequently need to raise the voltage of these devices, since they are pushing them harder, which also generates more heat.
Overclocking no longer makes the performance difference it used to. It will also void your CPU warranty, could cause complete system failure requiring component replacement, and can cause random system instability. For that reason, many of the frequency and voltage settings offered in this part of the BIOS should be left alone or set to AUTO. But if you do want to adjust them, click on the ADVANCED tab on the BIOS screen.
CPU External Freq. (MHz) : Be sure to set this in accordance with the specifications of your processor.
CPU Frequency Multiple Setting : AUTO.
CPU Frequency Multiple : Be sure to set this in accordance with the specifications of your processor.
Asus should have called this the CPU Multiplier. To understand what this means, realize that the CPU processes data at a different speed than the rest of your system. In this example, an AMD Athlon 2600 CPU is used, which runs at 2.133 GHz. It talks to the motherboard at 133.33 MHz, which is referred to as the Front Side Bus (FSB) speed. Therefore, 133.33 MHz (generally referred to as 133 MHz) is the FSB speed, while the CPU processes data at a multiple of 16 x 133.33 for a total of 2,133, or 2.133 GHz. So the multiplier is 16.
Through testing, AMD has determined - as have many independent magazines - that their 2.133 GHz CPU runs as fast as (or faster than) an Intel CPU rated at 2.6 GHz. Knowing that most consumers shop looking for large numbers to equate to performance, AMD had to come up with a way to convince consumers that even though their clock speed number was smaller, the processor's performance was the same or better than an Intel system with larger numbers. This explains why an AMD Athlon 2600 (as used in this example) actually runs at 2.1333 GHz and not the implied 2.6 GHz.
System Performance : Optimal.
CPU Interface : Optimal.
Memory Frequency : By SPD. Most memory-chip manufacturers include a Serial Presence Detect (SPD) chip, which reports to the computer's BIOS the size, data width, speed, and voltage of the installed memory. These settings are determined by the manufacturer to ensure maximum performance and reliability, so "By SPD" is considered a safe, recommended setting. By adjusting these settings yourself, you may be able to squeeze more performance out of your system, but if you're not careful, you might cause your system to constantly crash, not boot properly, or not boot at all.