In
computer architecture
In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the ...
, frequency scaling (also known as frequency ramping) is the technique of increasing a processor's
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
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
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
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
Electric energy consumption is the form of energy consumption that uses electrical energy. Electric energy consumption is the actual energy demand made on existing electricity supply for transportation, residential, industrial, commercial, and ot ...
in a chip is given by the equation
:
where ''P'' is power consumption, ''C'' is the
capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized ar ...
being switched per clock cycle, ''V'' is
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
, 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
Electric energy consumption is the form of energy consumption that uses electrical energy. Electric energy consumption is the actual energy demand made on existing electricity supply for transportation, residential, industrial, commercial, and ot ...
led ultimately to
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
's May 2004 cancellation of its
Tejas and Jayhawk Tejas was a code name for Intel's microprocessor, which was to be a successor to the latest Pentium 4 with the Prescott core and was sometimes referred to as Pentium V. Jayhawk was a code name for its Xeon counterpart. The cancellation of the proce ...
processors, which is generally cited as the end of frequency scaling as the dominant computer architecture paradigm.
Moore's Law 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 in the form of
multicore processors.
See also
*
Dynamic frequency scaling
Dynamic frequency scaling (also known as CPU throttling) is a power management technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly" depending on the actual needs, to conserve ...
*
Overclocking
In computing, overclocking is the practice of increasing the clock rate of a computer to exceed that certified by the manufacturer. Commonly, operating voltage is also increased to maintain a component's operational stability at accelerated sp ...
*
Underclocking
Underclocking, also known as downclocking, is modifying a computer or electronic circuit's timing settings to run at a lower clock rate than is specified. Underclocking is used to reduce a computer's power consumption, increase battery life, red ...
*
Voltage scaling
Dynamic voltage scaling is a power management technique in computer architecture, where the voltage used in a component is increased or decreased, depending upon circumstances. Dynamic voltage scaling to increase voltage is known as overvolting; d ...
References
{{reflist
Computer architecture
Central processing unit
fr:Fréquence du processeur