Intel Pentium 4 (and AMD Athlon XP) Processor

Intel's Pentium 4 CPUs are 'multiplier locked' meaning that it is not possible to change the processor's internal clock multiplier using the motherboard BIOS. This leaves us with only one option for overclocking Pentium 4 processors; increasing FSB speed.

Intel overclocking is thus quite a simple process.

1. Boot the computer into the BIOS screen.

2. Increase FSB speed in 5-10MHz increments. Reboot after each increment to ensure that the system can still boot into Windows properly.

3. If the system hangs, crashes or refuses to boot into Windows, increase the memory voltage slightly and retry. If this does not work, increase the chipset voltage and finally the core voltage. If this still does not work, reduce FSB settings slightly, reset the voltages to their previous values and try again.

4. Keep going until the system can no longer boot reliably into Windows, then back off to the previous 'safe' settings. Keep an eye on the processor's temperature in the BIOS. Remember that it should be under 70°C.

5. Benchmark the overclocked system and compare the results to the performance baseline established earlier. If the system does not complete the benchmarks or crashes, either reduce the FSB setting slightly or increase voltages to compensate and retry.

6. Depending on the current overclocked FSB speed, a memory divider can be used to try to achieve higher speeds. Note that the memory may not be the limiting factor, and if it is not, the divider will not help.

7. Once a fully benchmarked overclocked setting is achieved, run the Prime95 stress test for a couple of hours to verify that the system is generally stable. Enjoy the free additional performance!

AMD Athlon 64 Processor

Unlike Pentium 4 processors, AMD Athlon 64 CPUs are not completely multiplier locked. Regular Athlon 64's allow the internal multiplier to be reduced, while Athlon 64 FX processors allow complete control. This adds a level of flexibility to overclocking these CPUs, but the basic procedure remains the same. Instead of the FSB, we have motherboard clock speed but the equation remains the same: CPU multiplier x Motherboard Clock Speed = Processor speed in MHz.

The main difference to keep in mind when comparing Athlon 64 overclocking to Pentium4 overclocking is that Athlon 64 systems run slower in terms of MHz speed, but do a lot more work per clock cycle than the Intel competition. As far as this article is concerned, this means that upping the clock speed of the CPU is far more important than increasing memory speed. It also means that even if the memory divider has to be used to squeeze more MHz out of the processor, it will pay off.

In most Athlon 64 systems, the speed of the Hypertransport bus can also be adjusted, but this runs independently of the CPU and memory clock speeds, and is almost completely irrelevant for overclocking (or system performance in general).

1. Boot the computer into the BIOS screen.

2. Increase Motherboard Clock Speed or FSB speed in 5-10MHz increments. Reboot after each increment to ensure that the system can still boot into Windows properly.

3. If the system hangs, crashes or refuses to boot into Windows, increase the memory voltage slightly and retry. If this does not work, increase the chipset voltage slightly and try again, finally, increase the core voltage. If this still does not work, reduce FSB settings slightly, reset the voltages to their previous values and try again.

4. Keep going until the computer can no longer boot reliably into Windows, then back off to the previous safe settings. Keep an eye on the processor's temperature in the BIOS. Remember that it should be under 70°C to avoid limiting the overclocking potential and triggering the processor's thermal throttling feature.

5. Benchmark the overclocked system and compare the results to the performance baseline established earlier. If the system does not complete the benchmarks or crashes, either reduce the FSB setting slightly or increase voltages to compensate and retry.

6. Depending on the current overclocked FSB speed, a memory divider may be used to try to achieve higher speeds. Note that the memory may not be the limiting factor, and if it is not, the divider will not help.

7. Once a fully benchmarked overclocked setting is achieved, run the Prime95 stress test for a couple of hours to verify that the system is generally stable. Enjoy the free additional performance!