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Underclocking and overclocking a computer system

04 May 2010 at 15:38
Overclocking permits you to breath new life into an older system. However, not all computers are overclockable so make sure yours can overclock before coming to this article.

Abstract

In this tutorial, I will be explaining why overclocking and underclocking the central processing unit is good and why it is bad.

Power consumption

The obvious flaw with overclocking is down to power consumption levels involved. A standard Intel Core i7 in 2010 when this article was written had a thermal design power of 130W and a clock frequency of 2.66GHz (Core i7 920). Overclocking the system from 2.66GHz to 3GHz has an increase of 12% on the frequency which means that based on the formula:

P=CV2f

This formula shows that power is directly proportional to the voltage and frequency. The C is for capacitance, which does not vary in a CMOS transistor. If the voltage is changed, the power is increased by V2 instead of just rising with the voltage. Here's the problem. The CPU, in most cases, requires the voltage to be raised with the frequency to ensure system stability.

What do we do to combat this? Avoid raising the voltage too high, 1.75V to 2.25V is a 60% increase on the power consumption which is huge. That means if the CPU is consuming 30W, it will now consume 48W. This means when your system becomes unstable at the stock voltage you have probably reached the maximum power consumption for that voltage. An increase in voltage will then be required which means greater power consumption.

Performance

Of course it is true that there will be a performance gain from overclocking your processor, but is it worth the extra power consumption? Well yes, it is. Some games demand a lot more than a low end system has to offer, but overclocking the system can bring back life to the system in a way that no other improvement could offer.

Some custom system builders would choose a low end, cheap and relatively basic processor as the core of their build to keep costs down. They then overclock the system to its maximum and in some cases, the low end outperforms the higher end in a price-performance ratio.

Underclocking a system can have the inverse effect; i.e. performance will go down. With a low-end CPU, this can have incredibly draining effects on your system. The system may freeze up and shut down and worse, could fail to start correctly.

Underclocking looses performance at the price of reducing both heat and power. It normally comes from reducing the CPU frequency before the voltage. Back in the days of the Intel Pentium 4, a mobile iteration of the desktop CPU came to notebooks. The Pentium 4 Mobile worked by halving the voltage to reduce heat and power consumption, at the cost of performance and stability. Underclocking a higher end CPU, such as an i7 940 will allow you to reduce power consumption at the cost of performance on a much lower scale. Underclocking is something I have done before when my system was used for minor tasks.

Life span

Of course the life span of an overclocked CPU is shortened. This is due to the fact that each clock cycle is sped up to a level which causes more heat. This will cause the die in the CPU to crack from the excess heat eventually. The extra heat is generated from the extra power, which in turn is generated from the extra voltage and frequency. The TDP or thermal design power is the maximum heat that the CPU can dissipate. Most CPUs are either 95W or 130W.

Underclocked CPUs have a longer life span than even stock CPUs have. So if you are hoping to resell the CPU with a maximum condition, underclocking is a good idea.

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