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 |
