Intel has moved away from labelling its processors by clock speed. So which CPU is which? Our quick guide explains the new Pentium 4 and Celeron landscape.

If the names and numbers of computer parts cause you consternation, then Intel's recent move away from its straightforward method of labelling processors by clock speed may produce a less than calming effect on you. Coinciding with the release of its 915 and 925X Express chipsets, Intel will now drop the gigahertz rating from its model names in favour of a three-digit model number. For example, the 3.6GHz Pentium 4 is now called the Pentium 4 560. Similarly, Intel's budget Celeron desktop chips have adopted a 300-series model number.

Intel says that it's using model numbers to de-emphasise raw speed and shift the focus to other features that affect a processor's overall performance -- cache size, frontside bus speed and advanced technologies such as Hyper-Threading (found on some of its newer chips). There are some exceptions, however: older Northwood-core Pentium 4 chips won't adopt the model number and will continue to be listed by clock speed. And only some of the Pentium 4 chips built with the newer Prescott core will use the model-number naming scheme -- Prescott-core CPUs that use the older 875P and 865 chipsets will not.

Notebooks, too
In addition to the Pentium 4 500-series and Celeron 300-series chips on the desktop side, Intel is bringing the new model-number nomenclature to its mobile chips, too. Pentium M processors comprise the 700 series, mobile Pentium 4 processors the 500 series, and Celeron M processors the 300 series. If you're shopping for a notebook, you have even more features to consider, such as battery life and integrated wireless capability, which gives Intel's new model numbers perhaps even greater significance here.

And don't confuse Intel's new strategy with AMD's decision to rename its Athlon XP processors three years ago. AMD's model numbers were based on 'equivalent clock speeds' in an effort to emphasise that the overall performance of the lower-clocked Athlon chips matched up with their seemingly faster Pentium competitors.

GHz still matters
Of course, just because Intel isn't advertising the clock speeds of its processors as heavily doesn't mean you can ignore speed when shopping for a PC (or a CPU). Clock speed is still a very good indicator of a PC's overall performance. In fact, Dell, HP and Sony all list the new model number along with the clock speed of the Pentium 4s they offer for their desktops.

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