Editing Clock generator (section)

{{Short description|Device used to synchronize a circuit}}
{{No footnotes|date=March 2013}}
[[File:Clock Pulse Generator.png|thumb|[[Circuit diagram]] of a clock generator]]
[[Image:ICS 952018AF.jpg|thumb|upright=1.2|A desktop PC clock generator, based on the chip ICS 952018AF and 14.3 MHz resonator (on the left)]]
[[Image:Silego clock generator.JPG|thumb|upright=1.2|A laptop PC clock generator, based on the Silego chip]]
A '''clock generator''' is an [[electronic oscillator]] that produces a [[clock signal]] for use in synchronizing a circuit's operation. The output [[clock signal]] can range from a simple symmetrical [[Square wave (waveform)|square wave]] to more complex arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier.

The resonant circuit is usually a [[quartz]] [[piezoelectricity|piezo-electric]] [[crystal oscillator|oscillator]], although simpler [[tank circuit]]s and even [[RC circuit]]s may be used.

The [[amplifier]] circuit usually inverts the signal from the oscillator and feeds a portion back into the oscillator to maintain oscillation.

The generator may have additional sections to modify the basic signal. The [[Intel 8088|8088]] for example, used a 2/3 [[duty cycle]] clock, which required the clock generator to incorporate logic to convert the 50/50 duty cycle which is typical of raw oscillators.

Other such optional sections include [[frequency divider]] or [[clock multiplier]] sections. Programmable clock generators allow the number used in the divider or multiplier to be changed, allowing any of a wide variety of output frequencies to be selected without modifying the hardware.

The clock generator in a [[motherboard]] is often changed by computer enthusiasts to control the speed of a [[Central processing unit|CPU]], [[Front-side bus|FSB]], [[Graphics processing unit|GPU]] or [[Random-access memory|RAM]]. Typically the programmable clock generator is set by the [[BIOS]] at boot time to the selected value; although some systems have [[dynamic frequency scaling]], which frequently re-programs the clock generator.