A cpu also has a speed rating based on millions of cycles a second. One million cycles in a second is referred to as a megahertz. Megahertz is usually abbreviated Mhz. In general, the larger the megahertz rating, the faster the processor will be. A 100 Mhz Pentium will be faster than a 66 Mhz Pentium. This rating system is only accurate when you are comparing computers with the same type and generation of cpu. A 25 Mhz 486 is faster than a 33Mhz 386(!)