In
computer architecture, frequency scaling (also known as frequency ramping) is the technique of increasing a processor's
frequency so as to enhance the performance of the system containing the processor in question. Frequency ramping was the dominant force in commodity processor performance increases from the mid-1980s until roughly the end of 2004.
The effect of processor
frequency on computer speed can be seen by looking at the equation for computer program runtime:
:
where instructions per program is the total instructions being executed in a given program, cycles per instruction is a program-dependent, architecture-dependent average value, and time per cycle is by definition the inverse of processor frequency. An increase in frequency thus decreases runtime.
However,
power consumption in a chip is given by the equation
:
where ''P'' is power consumption, ''C'' is the
capacitance being switched per clock cycle, ''V'' is
voltage, and ''F'' is the processor frequency (cycles per second). Increases in frequency thus increase the amount of power used in a processor. Increasing processor
power consumption led ultimately to
Intel's May 2004 cancellation of its
Tejas and Jayhawk processors, which is generally cited as the end of frequency scaling as the dominant computer architecture paradigm.
Moore's Law
Moore's law is the observation that the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and projection of a historical trend. Rather than a law of physics, it is an empir ...
was
still in effect when frequency scaling ended. Despite power issues, transistor densities were still doubling every 18 to 24 months. With the end of frequency scaling, new transistors (which are no longer needed to facilitate frequency scaling) are used to add extra hardware, such as additional cores, to facilitate parallel computing - a technique that is being referred to as
parallel scaling.
The end of frequency scaling as the dominant cause of processor performance gains has caused an industry-wide shift to
parallel computing
Parallel computing is a type of computation in which many calculations or processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different fo ...
in the form of
multicore processors.
See also
*
Dynamic frequency scaling
*
Overclocking
*
Underclocking
*
Voltage scaling
References
{{reflist
Computer architecture
Central processing unit
fr:Fréquence du processeur