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Microprocessor Evolution

The 4004 CPU was the forerunner of all of today’s Intel offerings and, to date, all PC processors have been based on the original Intel designs. The first chip used in an IBM PC was Intel’s 8088. This was not, at the time it was chosen, the best available CPU, in fact Intel’s own 8086 was more powerful and had been released earlier. The 8088 was chosen for reasons of economics: its 8-bit data bus required less costly motherboards than the 16-bit 8086.

Also, at the time that the original PC was designed, most of the interface chips available were intended for use in 8-bit designs. These early processors would have nowhere near sufficient power to run today’s software.

The table below shows the generations of processors from Intel’s first generation 8088/86 in the late 1970s to the eighth-generation AMD Athlon 64, launched in the autumn of 2003:

Chronological Evolution of CPUs

Type/

Generation

 Year Data/

Address

bus width

 Level 1 Cache

(KB)

 Memory

bus speed

(MHz)

 Internal

clock

speed

(MHz)
8088/

First

 1979 8/20 bit None 4.77-8 4.77-8
8086/

First

 1978 16/20 bit None 4.77-8 4.77-8
80286/

Second

 1982 16/24 bit None 6-20 6-20
80386DX/

Third

 1985 32/32 bit None 16-33 16-33
80386SX/

Third

 1988 16/32 bit 8 16-33 16-33
80486DX/

Fourth

 1989 32/32 bit 8 25-50 25-50
80486SX/

Fourth

 1989 32/32 bit 8 25-50 25-50
80486DX2/

Fourth

 1992 32/32 bit 8 25-40 50-80
80486DX4/

Fourth

 1994 32/32 bit 8+8 25-40 75-120
Pentium/

Fifth

 1993 64/32 bit 8+8 60-66 60-200
MMX/

Fifth

 1997 64/32 bit 16+16 66 166-233
Pentium Pro/

Sixth

 1995 64/32 bit 8+8 66 150-200
Pentium II/

Sixth

 1997 64/32 bit 16+16 66 233-300
Pentium II/

Sixth

 1998 64/32 bit 16+16 66/100 300-450
Pentium III/

Sixth

 1999 64/32 bit 16+16 100 450-1.2GHz
AMD Athlon/

Seventh

 1999 64/32 bit 64+64 266 500-2.2GHz
Pentium 4/

Seventh

 2000 64/32 bit 12+8 400 1.4GHz-3.6GHz
AMD Athlon 64/

Eighth

 2003 64/64 bit 64+64 400 2GHz-2.4GHz

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