Till now, all processors were sold with a rating in megahertz or gigahertz. For instance, P4s come in 2.4GHz, 2.53GHz, 2.8GHz, 3.06GHz, etc. AMD’s Athlons are no longer marked with their true clock frequencies. In its place, AMD has adopted a marking scheme that describes the Pentium-equivalent speed. This description is known as P-rating.

For instance, an Athlon XP 1500+ originally runs at 1333MHz, but according to AMD it compares in performance to a Pentium 4 1500MHz. Whether this is actually the case is the subject of heated debate in the hardware community; some benchmarks back up AMD’s theory and some don’t. For comparison, check out the Athlon P-ratings and actual megahertz speeds in Table 2-1.

Remember that Table 2-1 indicates the speeds of processors based on AMD’s current Thoroughbred core. The newest Athlons, from the 2700+ and higher, support a 333MHz FSB, while previous ones support a 266MHz core. All support 333MHz and 400MHz DDR memory.