Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
Yes. but it works inside the Chip. externally you will give only few MHz Clock to the chip. Every Chip will have PLL block inbuilt and it will distribute the clock to other functional blocks. Mostly 2.5GHz represents only the chip core the speed.
You can't easily carry GHz signals on the PCB or through the processor socket so a lower speed is generated on the main board (typically around 200 - 300MHz) and it is multiplied up by a PLL and oscillator built on to the processors own silicon. On some processors there are "multiplier pins" which decide by how many times the motherboard clock is multiplied to give procesor clock, it's one of the ways 'overclockers' boosted system speeds. On most modern processors the manufacturer sets the multiplier internally and the only way to change speeds is to adjust the motherboard clock which can also have other consequences to peripheral devices whch also use it.