How to overclock Intel Core 2 Duo/Quad Processors

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Written by Ben Rogers, a freelance IT technician from North Devon, England. He has been into computers in a big way for quite a number of years now and loves overclocking, He enjoys tweaking PCs and seeing how fast they can go and benchmarking them too! You can see more of his work at his website, Noshins.

Getting the best performance

To get the best performance out of an Intel LGA775, either dual or quad core you will require to have the memory in sync with the FSB, which allows for maximum memory bandwidth.

Modern computers run a lot faster and smoother when they are both ran in sync. This often means running the FSB way above what it is rated for which can often require the chipset voltage to be upped a notch or two to achieve absolute stability. You will require RAM that can meet the desired FSB speed, for example PC6400 runs at 800MHz so it can cope with a 400MHz FSB.

Overclocking Principles:

The basic principle of overclocking starts with focusing on the FSB and raising it in small amounts until the system gets unstable, then upping the CPU voltage (Vcore) a notch or two before trying again,

The best way to start overclocking is by raising the FSB by 5MHz increments and testing for stability using Orthos every time that you do so.Orthos stress test the CPU, finding any errors in calculation. If the system is wildly unstable the machine will lock up when Orthos is ran. Orthos is freeware, will test 4 core CPUs and is very useful for stress testing and finding instability within cpus when overclocking

You can also use CPU-Z to monitor the processor frequency (MHz), the bus speed(FSB), memory timings and speed at which they are set.

Stress Testing:

If the PC locks up when running Orthos go back into the BIOS and up the Vcore a knotch or two and test again. If it still locks up determine whether it took the same amount of time to lock up since you upped the Vcore, if it did try losening the memory timings a bit or lowering the RAM divider to take the RAM out of the equation. If it takes longer to lock up once you have upped the Vcore you may be on to a winner, the CPU voltage may not be enough for the clock speed you are trying to run.

Up it another notch or two but be careful:

• Not to exceed 1.40v for a 45nm CPU or 1.5v for a 65nm CPU, else you seriously risk damaging it.
• Watch the temperatures using Speedfan, making sure the CPU cores don’t go above 60ºC.

If it is nearly at 60ºC then it is time to invest in a better heatsink/fan combo. Aim for the CPU temperature to be in the mid 30s when the CPU is idle and 50ºC full load, with good air cooling this can be achieved even with a hefty overclock providing you dont go mad on the voltage.

If you are overclocking and you up the FSB too much you may find yourself in a very awkward position, or at least that may be how it seems if the screen does not come on when you save settings from the BIOS and exit!

No POST (Power on Self Test):

This can dealt with easily by referring to the user manual for the motherboard and locating the clear CMOS jumper which is usually near the CMOS battery and moving the jumper to the clear CMOS position (the opposite two pins to where it is normally) and leaving it on clear for 30 seconds to a minute with the power plug removed from the back of the PSU.

Put it back to its original position, plug back the power cord into the power supply and trying booting again.

If your memory requires higher than default voltage, you may have to remove a stick in order to boot when you get no POST.

The Sweet Spot

A sweet spot for a lot of Core 2 Duo/Quad is to use a 400MHz FSB with PC6400, keeping the RAM in sync to achieve a nice and easy overclock if all goes to plan.

Take note though that some lower-end motherboards will simply not be able to achieve 400MHz FSB, so a lower overal overclock is to be expected with such setups, however a suitable overclock will be acheiveable with a bit of tweaking.

Memory Timings:

Memory timings can be an important part of overclocking but thesedays with the latest hardware they do not make as much difference as they used to in the AMD Athlon XP Socket A days, however, it is still worth bearing in mind that they can effect performance somewhat and tweaking them can bring out more speed from your system. They can be changed in the BIOS or in Windows by using a program called MemSet providing you have a supported chipset.

You can find MemSet here:

http://www.tweakers.fr/download/MemSet40.zip

When tweaking the memory first try changing the CAS latency down a knotch from say CL6 to CL5 and see if it works, then try the same for the other timings.

Conclusion:

I invite you to share any experience that you had overclocking, including tips and recommendations that you have for someone who’s tempted to try, yet scared of the risks involved. To everyone, good luck with any overclocking you may be carrying out!