Rating CPUs, CPU speed, memory addresses

Common CPUs

IBM and IBM-compatible computers manufactured today use a microprocessor chip made by Intel or one of its competitors. Early CPUs by Intel were identified by model numbers: 8088, 8086, 80286, 386, and 486.

The next CPU introduced after the 486 was named the Pentium, and all Intel CPUs after that include Pentium in their name. The model numbers can be written with or without the 80 prefix and are sometimes preceded with anias in 80486, 486, or i486.

The name Pentium comes from the word pente, the Greek word for five, which Intel chose after a legal battle with two competitors, AMD and Cyrix. AMD and Cyrix won rights to continue using the X86 chip names, but are not allowed to use the word “Pentium” to name their CPUs.

Rating CPUs

You need to know how to identify a CPU installed in a system and what performance to expect from that CPU. The following attributes are used to rate CPUs:

CPU speed measured in megahertz - The first CPU used in an IBM PC was the 8088, which worked at about 4.77 MHz, or 4,770,000 clock beats per second. An average speed for a new CPU today is about 550 MHz, or 550,000,000 beats per second.

Efficiency of the programming code - Permanently built into the CPU chip are programs that accomplish fundamental operations, such as how to compare or add two numbers. Less efficient CPUs require more steps to perform these simple operations than more efficient CPUs. These groups of instructions are collectively called the “instruction set.”

Word size, sometimes called the internal data path size - Word size is the largest number of bits the CPU can process in one operation. Word size ranges from 16 bits (2 bytes) to 64 bits (8 bytes).

Data path - The data path, sometimes called the external data path size, is the largest number of bits that can be transported into the CPU. The size of the data path is the same as the system bus size, or the number of bits that can be transported along the bus at one time. (The data path ranges from 8 bits to 64 bits.) The word size need not be as large as the data path size; some CPUs can receive more bits than they can process at one time.

Maximum number of memory addresses - A computer case has room for a lot of memory physically housed within the case, but a CPU has only a fixed range of addresses that it can assign to this physical memory. How many memory addresses the CPU can assign limits the amount of physical memory chips that the computer can effectively use. The minimum number of memory addresses a CPU can use is one megabyte (where each byte of memory is assigned a single address).

The amount of memory included with the CPU - Some CPUs have storage for instructions and data built inside the chip housing. This is called internal cache, primary cache, level 1, or L1 cache.

Multiprocessing ability - Some microchips are really two processors in one and can do more than one thing at a time. Others are designed to work in cooperation with other CPUs installed on the same systemboard.

Special functionality – An example of this is special purpose CPUs, such as the Pentium MMX CPU, which is designed to manage multimedia devices efficiently.