 - In a computer, clock speed refers to the number of
pulses per
second generated by an oscillator that sets the tempo for the processor. Clock speed is
usually
measured in MHz (megahertz, or
millions of pulses
per second) or GHz (gigahertz, or billions of pulses per second).
Today's personal computers run at a clock speed in the hundreds of megahertz and some exceed one gigahertz.
The clock
speed is determined by a quartz-crystal circuit, similar to those used in
radio
communications equipment.
Computer clock speed has been roughly doubling every
year. The Intel
8088, common in computers around the year 1990, ran at 4.77 MHz. The 1 GHz mark was passed in the year 2000.
Clock speed is one measure of computer "power," but
it is not
always directly proportional to the performance level. If you double the
speed of
the clock, leaving all other hardware unchanged, you will not necessarily
double the
processing speed. The type of microprocessor, the bus architecture, and
the nature
of the instruction set all make a difference. In some applications, the
amount of random access memory (RAM) is important,
too.
Some processors execute only one instruction per clock
pulse. More
advanced processors can perform more than one instruction per clock
pulse. The
latter type of processor will work faster at a given clock speed than the
former type.
Similarly, a computer with a 32-bit bus will work faster at a given
clock speed
than a computer with a 16-bit bus. For these reasons, there is no
simplistic,
universal relation among clock speed, "bus speed," and millions of
instructions
per second (MIPS).
Excessive clock speed can be detrimental to the operation of a
computer.
As the clock speed in a computer rises without upgrades in any of the
other
components, a point will be reached beyond which a further increase in
frequency will
render the processor unstable. Some computer users deliberately increase
the clock
speed, hoping this alone will result in a proportional improvement in
performance, and are
disappointed when things don't work out that way.
| LAST UPDATED: |
29 May 2001
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