Hardware Reference
In-Depth Information
Most frequency synthesizer chips used on PC motherboards are made by a handful of
companies, including Integrated Device Technology ( www.idt.com ; formerly Integrated
Circuit Systems) and Cypress Semiconductor ( www.cypress.com ; formerly International
Microcircuits Inc. [IMI]). These chips use phased locked loop (PLL) circuitry to generate
synchronized processor, PCI, AGP, and other bus timing signals that are derived from a
single 14.318MHzcrystal. Thecrystal andfrequency synthesizer chipareusually situated
near the processor and main chipset component of the motherboard.
The amazing thing about these chips is that most of them are programmable and ad-
justable,sotheycanchangetheirfrequencyoutputsviasoftware,whichresultsinthesys-
tem running at different speeds. Because all CPUs are based on the speed of the CPU bus,
when you change the CPU bus speed generated by the frequency synthesizer chip, you
canchangethespeedofyourprocessor.BecausethePCI,AGP,andmemorybusesareof-
ten synchronized with the speed of the processor bus, when you change the processor bus
speed by a given percentage, you also change the speed of those other buses by the same
percentage. The software to accomplish this is built into the BIOS Setup menus of most
modern motherboards.
Overclocking Tips
Most modern motherboards automatically read the CPU and memory components to de-
termine their proper speed, timing, and voltage settings. Originally, these settings were
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