CPU : Computer Hardware Buyers’ Glossary

by Roedy Green ©1997-2008 Canadian Mind Products
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CPU

The CPU is the part of the computer that does the calculations. A clock beats out a rhythm like a slave driver in a Roman oar-driven ship. The CPU does some calculation on each beat of the clock. The faster the clock beats the faster the work gets done. Roughly speaking then a 200 MHz CPU (the clock beats 200,000,000 times a second) will work twice as fast as one that works at 100 Mhz. In practice the whole computer will be considerably less than twice as fast because the other parts of the computer e.g. the RAM, hard disk etc. are no faster. Different CPU chips, even at the same clock rate, perform differently. More expensive CPU chips are designed to do more work per clock beat. They may do this by clever circuitry or by taking bigger hunks of data to process at once, or by doing more than one calculation per clock beat. Here are the Intel line of CPU chips used in MS-DOS/Windows personal computers ordered from slowest to fastest. People tend to focus too much on raw CPU speed. More RAM, faster hard disk, a smarter video card, faster RAM, or a bigger SRAM cache are often better places to spend your money to get an overall faster computer.

Most new computers sold are in the 2 to 3 gigahertz (2,000 to 3,000 Mhz) range. The two leading manufacturers are AMD and Intel. Usually a AMD CPU of the same MHz rating is faster than the equivalent Intel CPU because it gets more done per clock cycle. AMD uses model numbers to account for this. E.g. the Athlon 1600+ is roughly equivalent to a Pentium IV 1.6 gigahertz CPU, though it runs at only a 1.4 gigahertz clock speed. They roughly approximate the power of the equivalent Intel CPU. On the other hand, some software is tuned for Intel and may not work as fast on AMD or may not work at all. This is less of a problem than it was in past. Clock speed is misleading. A CPU with double the clock speed may run only marginally faster, because it spends most of its time waiting for RAM which is no faster. A dual CPU may run only marginally faster than a single one because the two CPUs have to keep waiting for each other for common hunks of RAM.

Intel’s value line is called Celeron. AMD’s value line is called Duron.

Intel’s premium line is called Xeon, and AMD’s premium line is called Athlon.

Intel’s 64 bit server line is called Itanium. AMD’s 64-bit server line is called Opteron.

Intel chip	bits grabbed at once	bits calculated at once
Intel 8088 (XT)	8	16
Intel 8086	16	16
Intel 80286 (AT)	16	16
Intel 80386sx	16	32
Intel 80386dx	32	32
Intel 80486	32	32
Intel Pentium (586)	64	32
Intel Pentium Pro (686)	64	32
Intel Pentium II (796)	64	32
Intel Pentium III, AMD Duron	64	32
Intel Pentium IV, AMD Athlon	64	32
Intel Itanium	128	64
AMD Opteron	128	64

CPUs prices are sometimes quoted without fans. Cooling fans mounted on the CPU are manadatory. If one is not included, you will have to buy one separately for about $20.00 CAD

AMD
Athlon
benchmarks: speed comparisons
Celeron
fan
hyperthreading
Intel
Itanium
motherboard
Opteron
Pentium
Sempron
socket

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