| In the table below, you see a number of the most common older CPUs. You can see how they are designed regarding clock speed and bus width. The last column shows their Norton Speed Index (SI). That is a relative number, which can be used to compare different CPUs. It is not used for modern CPUs. |
| CPU | CPU speed | Clock
doubling |
System bus
speed |
Data width | SI |
| 8086 | 4.77 MHz | 1 | 4.77 MHz | 16 bit | 1 |
| 80286 | 12 MHz | 1 | 12 MHz | 16 bit | 8 |
| 80386DX | 25 MHz | 1 | 25 MHz | 32 bit | 40 |
| 486 DX2-66 | 66 MHz | 2 | 33 MHz | 32 bit | 142 |
| 5x86-133 | 133 MHz | 4 | 33 MHz | 32 bit | 288 |
| Pentium 75 | 75 MHz | 1.5 | 50 MHz | 64 bit | 235 |
| Pentium 90 | 90 MHz | 1.5 | 60 MHz | 64 bit | 278 |
| Pentium 100 | 100 MHz | 1.5 | 66 MHz | 64 bit | 305 |
| Pentium 133 | 133 MHz | 2 | 66 MHz | 64 bit | 420 |
| Pentium 166 | 166 MHz | 2.5 | 66 MHz | 64 bit | 527 |
| Pentium 200 | 200 MHz | 3 | 66 MHz | 64 bit | 629 |