Hardware Reference
In-Depth Information
its true maximum speed. I don't normally recommend overclocking for a novice, but if you are
comfortable playing with your system settings, and you can afford and are capable of dealing with
potential consequences, overclocking might enable you to get another 10%-20% or more
performance from your system.
Overclocking is usually applied to the processor, but it can also be applied to other components in the
system, including memory, video cards, bus speeds, and more.
When chips run faster, they run hotter, so cooling upgrades and modifications usually go hand-in-hand
with overclocking. Systems that run cool tend to be more stable and more reliable, so even if you
don't overclock your system, ensuring that it runs cool is essential for trouble-free operation. Many
systems are not properly designed or configured for optimal cooling even at their standard speeds,
much less when overclocked.
Overclocking PCs dates all the way back to the original 4.77MHz IBM PC and 6MHz AT systems of
the early 1980s. In fact, IBM made overclocking the AT easy because the quartz crystal that
controlled the speed of the processor was socketed. You could obtain a faster replacement crystal for
about a dollar and easily plug it in. The first several editions of this topic covered how to perform
this modification in detail, resulting in a system that was up to 1.5 times faster than it started out.
Modern systems allow overclocking without replacing any parts by virtue of programmable timer
chips and simple and easy-to-change BIOS Setup options. Some processors, such as Intel Extreme
Edition and AMD Black Edition processors, are especially suited to overclocking because they
feature unlocked core multipliers. However, some overclocking is possible with almost any
processor.
Quartz Crystals
To understand overclocking, you need to know how computer system speeds are controlled. The main
component controlling speed in a computer is a quartz crystal. Quartz is silicon dioxide (SiO
2
) in
crystalline form. Oxygen and silicon are the most common elements on earth (sand and rock are
mostly silicon dioxide), and computer chips are made mainly from silicon. Quartz is a hard,
transparent material with a density of 2649 kg/m
3
(1.531 oz/in
3
) and a melting point of 1750°C
(3,182°F). Quartz is brittle but with a little bit of elasticity, which is perhaps its most useful attribute.
In crystalline form, quartz can generate regular and consistent signal pulses to regulate electronic
circuits, similar to the way a metronome can regulate music. Quartz crystals are used because they are
piezoelectric
, which is defined as having a property that generates voltage when subjected to
mechanical stress. The opposite is also true—that is, quartz generates mechanical stress or movement
when subjected to a voltage. Piezoelectricity was discovered by Pierre and Jacques Curie in 1880,
and it is the essential feature of quartz that makes it useful in electronic circuits.
Piezoelectricity works two ways, meaning that if a voltage is generated when you bend a crystal or
apply voltage to a crystal, it bends (contracts, expands, or twists) in a similar fashion. Although the
crystal is mostly brittle in nature, it is still somewhat elastic, such that any deformation tends to snap
back and then occur again, resonating or vibrating at a natural frequency as long as the voltage is
present. Much like a tuning fork or the pipes in an organ, the natural resonant frequency depends on
the size and shape of the crystal. In general, the smaller and thinner it is, the faster it vibrates.
The actual movement is exceedingly small, on the order of 68 nanometers (billionths of a meter) per
centimeter, which in a normal crystal is only a few atoms in length. Although the movement is small,
