Intel
Intel classifies its CPUs using a series of numbers. 3xx, 4xx, 5xx, 6xx and
7xx of which 7xx denominates the highest end products. Generally, the higher
the number, the faster the CPU and the more expensive. Usually, models and
ratings correspond.
• 3xx Series: Intel Celeron (L2-128KB)
• 4xx Series: Intel Celeron D (L2-512KB)
• 5xx Series: Intel Pentium 4 / Celeron D (L2-1MB)
• 6xx Series: Intel Pentium 4 / Pentium 4 XE (L2-2MB)
• 7xx Series: Intel Pentium 4 XE
• 8xx Series: Intel Pentium D
• 9xx Series: Intel Pentium D
The number followed by suffix J signifies XD technology.
E.g. Intel Pentium 4 3.0GHz L2-1MB with HT – Intel Pentium 4 530J
There is also the Core 2 Duo range out at the moment—it’s naming scheme
is relatively normal, except for the models ending with 50, they have 1333mhz
FSB.
• E6300/E6320: 1.86Ghz, 2MB L2 Cache (E6320 has 4MB), 1066MHz FSB
• E6400/E6420: 2.13Ghz, same as above
• (new) E6540: 2.33Ghz, 4MB L2 Cache, 1333MHZ FSB
• (new) E6550: 2.33Ghz, same as above
• E6600: 2.4Ghz, 4MB L2 Cache, 1066MHZ FSB
• E6700: 2.66Ghz, same as above
• (new) E6750: 2.66Ghz, 4MB L2 Cache, 1333MHZ FSB
• (new) E6850: 3.0Ghz, same as above
• X6800: 2.93Ghz, same as above except multiplier unlocked

AMD
AMD CPUs are even more confusing in classification. The AMD Athlon CPU
rating are not of the actual clock speed but rather the equivalence bench mark
performance corresponding to a comparison to the AMD Athlon Thunderbird
1.0Ghz. The conversion Table is as follows:
• AMD Athlon 1500+ = Actually runs at 1.33 GHz
• AMD Athlon 1600+ = Actually runs at 1.40 GHz
• AMD Athlon 1700+ = Actually runs at 1.47 GHz
• AMD Athlon 1800+ = Actually runs at 1.53 GHz
• AMD Athlon 1900+ = Actually runs at 1.60 GHz
• AMD Athlon 2000+ = Actually runs at 1.67 GHz
• AMD Athlon 2100+ = Actually runs at 1.73 GHz
• AMD Athlon 2200+ = Actually runs at 1.80 GHz
• AMD Athlon 2400+ = Actually runs at 1.93 GHz
• AMD Athlon 2500+ = Actually runs at 1.833 GHz
• AMD Athlon 2600+ = Actually runs at 2.133 GHz
• AMD Athlon 2700+ = Actually runs at 2.17 GHz
• AMD Athlon 2800+ = Actually runs at 2.083 GHz
• AMD Athlon 3000+ = Actually runs at 2.167 GHz
• AMD Athlon 3200+ = Actually runs at 2.20 GHz
You may wish to purchase a high end AMD64/EM64T (AMD and Intel,
respectively) processor, which provides support for 64-bit operating systems
(eg. Windows XP Professional 64-bit Edition). Most 64-bit processors are
backwards-compatible with 32-bit operating systems and applications.. Given
the huge expansion in addressable memory afforded by the transition from 32-
bit to 64-bit (a 32-bit address space tops out at 4 Gigabytes while a 64-bit space
encompasses 17,179,869,184 Gigabytes) 64 bit operating systems are the wave
of the future. For the time being though, given the enormous quantity of 32-bit
software out there, and the limited advantages of 64-bit as of yet, the move is
likely to be a slow one.