Computer retailers describe the performance of their machines in terms of [[CPU]] [[Speed]] (in MHz or GHz). This refers to the numbercycles ofper instructionssecond of the Centralmain Processing Unitclock (CPU)megahertz canor performMHz eachis secondmillons, (in millionsgigahertz or billionsGHz respectivelyis billions). HoweverthisIt isdoes onlynot oneindicate of athe number of factorsinstructions. thatimpactSome onCPUs theexecute performanceless ofthan one instruction per clock. Some "super scalar" CPUs execute more than one instruction aper machineclock.
