Until recently, Intel had steadfastly used speed (in MHz and GHz) to name the various models in its processor lines. This used to be the rule for all processor manufacturers, since the computer buying public was used to the equation (faster processor name) = (faster computer).

AMD ditched this train of thought in 2001 when the company introduced the Athlon XP+ line of processors. Instead of identifying these chips by figures in GHz, AMD slapped on a 'Performance Rating' number which was intended to indicate the processors' relative performance as compared to an older line of Athlon CPUs.

This system was adopted since the XP+ line had considerably lower clock speeds than comparable Intel Pentium 4 processors. In all cases, the AthlonXP processors were comparable or superior in performance despite a dramatic difference in GHz figures between competing AMD and Intel CPUs. AMD reasoned correctly that the majority of the buying public would always choose the processor with the fastest sounding name, so the PR naming scheme (1800+, 3200+, etc.) was born and still lives on in the Athlon 64 processor line.

With the move to socket 775, Intel has also rebranded its Pentium 4 processors which were otherwise hitting the upper limits in terms of speed. The reason, as AMD figured out a while ago, is that users will not keep upgrading if the processors' names do not reflect a speed increase. The concept of ever increasing gigahertz values and computer speed being linked together is still firmly in the minds of consumers.... just like a 2006 Ford car just has to be 'better' than a 2005 Ford.

By switching to model names that are not related to speed, Intel has bought itself time to tinker with the processor lines. One upcoming change is the moving of Pentium M processor variants to the desktop. As these are much lower speed in terms of GHz speed (while performing equivalent work), this naming change makes sense for the future.

The new Intel naming scheme works like this:

Intel Pentium 4 processor 5xx = Pentium 4 processors with hyperthreading, 800Mhz FSB and 1MB of level 2 cache memory. The last two digits indicate speed. For example: 520 = 2.8GHz, 530 = 3.0 GHZ, 540 = 3.2GHz, etc.

Intel Celeron D processors 3xx = Celeron processors at 533Mhz FSB with 256K L2 cache memory. The last two digits indicate speed: 320 = 2.4 GHz, 325 = 2.53GHz, 330 = 2.66GHz, etc.

Intel Pentium 4 M processor 7xx = Pentium 4 M processor with 2MB of Level 2 cache memory and 400MHz FSB. The last two digits indicate speed: 715 = 1.50GHz, 725 = 1.60GHz, 735 = 1.70GHz, etc.