Clock rate: Difference between revisions

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<!-- [[File:MicroproceorMicroprocessor clock speed, OWID.svg|thumb|400px|Microprocessor clock speed over time]] -->

In [[computing]], the '''clock rate''' or '''clock speed''' typically refers to the [[frequency]] at which the [[clock generator]] of a [[MicropcessorMicroprocessor|procesorprocessor]] can generate [[Clock gnalsignal|pulses]], which are used to [[Synchronization (computer science)|synchronize]] the operations of its components,<ref>{{FOLDOC|new=yes|Clock}}</ref> and is used as an indicator of the processor's speed. It is measured in ''clock cycles per second'' or its equivalent, the [[International System of UntsUnits|SI]] unit of frequency [[hertz]] (Hz).

The clock rate of the first generation of computers was measured in hertz or kilohertz (kHz), the first [[personal computer]]s (PCs) to arrive throughout the 1970s and 1980s had clock rates measured in megahertz (MHz), and in the 21st century the speed of modern [[Central processing unit|CPU]]s is commonly advertised in gigahertz (GHz). This metric is most useful when comparing processors within the same family, holding constant other features that may affect [[Computer perfanceperformance|performance]]. [[Video card]] and CPU manufacturers commonly select their highest performing units from a manufacturing batch and set their maximum clock rate higher, fetching a higher price.{{citation nd|date=November 2019}}

=== Binning ===

Manufacturers of modern processors typically charge premiumhigher prices for processors that operate at higher clock rates, a practice called [[Product binning|binning]]. For a given CPU, the clock rates are determined at the end of the manufacturing process through actual testing of each processor. Chip manufacturers publish a "maximum clock rate" specification, and they test chips before selling them to make sure they meet that specification, even when executing the most complicated instructions with the data patterns that take the longest to settle (testing at the temperature and voltage that runsgives the lowest performance). Processors successfully tested for compliance with a given set of standards may be labeled with a higher clock rate, e.g., 3.50&nbsp;GHz, while those that fail the standards of the higher clock rate yet pass the standards of a lesserlower clock rate may be labeled with the lesserlower clock rate, e.g., 3.3&nbsp;GHz, and sold at a lower price.<ref>[{{cite patent|country=US|number=6826738|title=Optimization of die placement on wafers|url=http://www.google.com/patents/US6826738]}}.</ref><ref>{{cite [patent|country=US|number=6694492|title=Method and apparatus for optimizing production yield and operational performance of integrated circuits|url=http://www.google.com/patents/US6694492]}}.</ref>

The clock rate of a CPU is normally determined by the [[frequency]] of an [[Crystal oscillator|oscillator crystal]]. Typically a crystal oscillator produces a fixed [[sine wave]]—the frequency reference signal. Electronic circuitry translates that into a [[square wave]] at the same frequency for digital electronics applications (or, inwhen using a [[CPU multiplier]], some fixed multiple of the crystal reference frequency). The [[clock distribution network]] inside the CPU carries that [[clock signal]] to all the parts that need it. An [[Analog-to-digital converter|A/D Converter]] has a "clock" pin driven by a similar system to set the [[sampling rate]]. With any particular CPU, replacing the crystal with another crystal that oscillates at half the frequency ("[[underclocking]]") will generally make the CPU run at half the performance and reduce [[waste heat]] produced by the CPU. Conversely, some people try to increase performance of a CPU by replacing the oscillator crystal with a higher frequency crystal ("[[overclocking]]").<ref>{{Cite web |url=http://www.tomshardware.com/reviews/overclocking-guide-part-1,1379.html |title=Overclocking Guide Part 1: Risks, Choices and Benefits : Who Overclocks? |first1=Thomas |last1=Soderstrom |date=11 December 2006 |quote="Overclocking" early processors was as simple{{Snd}} and as limited{{Snd}} as changing the discrete clock crystal ... The advent of adjustable clock generators has allowed "overclocking" to be done without changing parts such as the clock crystal.}}</ref> However, the amount of overclocking is limited by the time for the CPU to settle after each pulse, and by the extra heat created.

The first fully mechanical analog computer, the [[Z1 (computer)|Z1]], operated clock frequency at 1&nbsp;Hz (cycle per second) clock frequency and the first electromechanical general purpose computer, the [[Z3 (computer)|Z3]], operated at a frequency of about 5–10&nbsp;Hz. The first electronic general purpose computer, the [[ENIAC]], used a 100&nbsp;kHz clock in its cycling unit. As each instruction took 20 cycles, it had an instruction rate of 5&nbsp;kHz.

The first commercial PC, the [[Altair 8800]] (by MITS), used an Intel 8080 CPU with a clock rate of 2&nbsp;MHz (2 million cycles per second). The original [[IBM Personal Computer|IBM PC]] (c. 1981) had a clock rate of 4.77&nbsp;MHz (4,772,727 cycles per second). In 1992, both Hewlett-Packard and Digital Equipment Corporation (DEC) exceeded 100&nbsp;MHz with [[RISC]] techniques in the PA-7100 and AXP 21064 [[DEC Alpha]] respectively. In 1995, [[Intel Corporation|Intel's]] [[P5 (microarchitecture)|P5]] [[Pentium (brand)|Pentium]] chip ran at 100&nbsp;MHz (100 million cycles per second). On March 6, 2000, [[Advanced Micro Devices|AMD]] demonstrated passing the 1&nbsp;GHz milestone a few days ahead of Intel shipping 1&nbsp;GHz in systems. In 2002, an Intel [[Pentium 4]] model was introduced as the first CPU with a clock rate of 3&nbsp;GHz (three billion cycles per second corresponding to ~ 0.33 [[nanosecond]]s per cycle). Since then, the clock rate of production processors has increased more slowly, with performance improvements coming from other design changes.

Set in 2011, the [[Guinness World Record]] for the highest CPU clock rate is 8.42938&nbsp;GHz with an [[Overclocking|overclocked]] AMD FX-8150 [[Bulldozer (microarchitecture)|Bulldozer]]-based chip in an [[Liquid helium|LHe]]/[[Liquid nitrogen|LN2]] cryobath, 5&nbsp;GHz [[Air cooling|on air]].<ref>{{Cite web|url=https://www.guinnessworldrecords.com/world-records/98281-highest-clock-frequency-achieved-by-a-silicon-processor|title = Highest clock frequency achieved by a silicon processor}}</ref><ref>{{cite web |first=Marco |last=Chiappetta |date=23 September 2011 |url=http://hothardware.com/News/AMD-Breaks-Frequency-Record-with-Upcoming-FX-Processor/ |title=AMD Breaks 8&nbsp;GHz Overclock with Upcoming FX Processor, Sets World Record with AMD FX 8350 |publisher=HotHardware |access-date=2012-04-28 |archive-date=2015-03-10 |archive-url=https://web.archive.org/web/20150310020437/http://hothardware.com/News/AMD-Breaks-Frequency-Record-with-Upcoming-FX-Processor |url-status=dead }}</ref> This is surpassed by the [[CPU-Z]] [[overclocking]] record for the highest CPU clock rate at 8.79433&nbsp;GHz with an AMD FX-8350 [[Piledriver (microarchitecture)|Piledriver]]-based chip bathed in [[Liquid nitrogen|LN2]], achieved in November 2012.<ref>{{Cite web |title=CPU-Z Validator – World Records |url=https://valid.x86.fr/records.html|title=CPU-Z Validator - World Records}}</ref><ref>{{Cite web |title=8.79GHz FX-8350 is the Fastest Ever CPU &#124; ROG – Republic of Gamers Global |url=https://rog.asus.com/articles/crosshair-motherboards/8-79ghz-fx-8350-is-the-fastest-ever-cpu/|title=8.79GHz FX-8350 is the Fastest Ever CPU &#124; ROG - Republic of Gamers Global}}</ref> It is also surpassed by the slightly slower AMD FX-8370 overclocked to 8.72&nbsp;GHz which tops ofoff the [[HWBOT]] frequency rankings.<ref name=James>{{cite news |last=James |first=Dave |date=16 December 2019 |title=AMD’sAMD's Ryzen rules overclocking world records… but can’tcan't beat a 5 year-old chip|url=https://www.pcgamesn.com/amd/cpu-overclocking-world-records |work= pcgamesn |access-date=23 November 2021}} </ref><ref name=HWBOTranks>{{cite web |url=https://hwbot.org/benchmark/cpu_frequency/rankings#start=0#interval=20 |title=CPU Frequency: Hall of Fame |website= hwbot.org |publisher=HWBOT |access-date=23 November 2021}}</ref> These records were broken in late 2022 when an Intel Core i9-13900K was overclocked to 9.008 GHz.<ref name=White>{{cite news |last= White |first=Monica J |date=22 December 2022 |title= Overclockers surpassed the elusive 9GHz clock speed. Here's how they did it

The highest [[Dynamic frequency scaling|base clock]] rate on a production processor is the [[IBMRaptor zEC12 (microprocessor)Lake|IBM zEC12i9-14900KS]], clocked at 56.52&nbsp;GHz, which was released in AugustQ1 20122024.<ref>{{Cite web |title=Products formerly Raptor Lake |url=https://www.intel.com/content/www/us/en/products/sku/codename/215599/products-formerly-raptor-lake.html |access-date=2024-07-05 |website=www.intel.com}}</ref>

== Research ==

The first fully reversible CPU, the Pendulum, was implemented using standard CMOS transistors in the late 1990s at MITthe Massachusetts Institute of Technology.<ref>

The clock rate of a CPU is most useful for providing comparisons between CPUs in the same family. The clock rate is only one of several factors that can influence performance when comparing processors in different families. For example, an IBM PC with an [[Intel 80486]] [[Central processing unit|CPU]] running at 50&nbsp;MHz will be about twice as fast (internally only) as one with the same CPU and memory running at 25&nbsp;MHz, while the same will not be true for MIPS R4000 running at the same clock rate as the two are different processors that implement different architectures and microarchitectures. Further, a "cumulative clock rate" measure is sometimes assumed by taking the total cores and multiplying by the total clock rate (e.g. duala dual-core 2.8&nbsp;GHz beingprocessor consideredrunning processorat a cumulative 5.6&nbsp;GHz). There are many other factors to consider when comparing the performance of CPUs, like the width of the CPU's [[Bus (computing)|data bus]], the latency of the memory, and the [[CPU cache|cache]] architecture.