The following are the theoretical maximum speeds for the busses.
| Bus name | Mbytes/sec |
|---|---|
| SCSI-1 | 5 |
| ISA | 8 |
| SCSI-2 | 10 |
| PCMCIA | 20 |
| IDE DMA33 | 33 |
| Ultra2 SCSI | 40 |
| IDE DMA66 | 66 |
| PC-Card | 132 |
| PCI 2.0 | 132 |
| PCI 2.1 | 264 |
| PCI 2.2 | 528 |
| Serial | 0.1 |
| Parallel Port | 0.1 |
| USB 1.0 | 1.5 |
| IEEE 1394 | 12.5-50 |
| USB 2.0 | 60 |
| IEEE 1394b | 25-100 |
The bus speed is the number of times per second that the bus transfers some data. The width is the number of bits
of data that are transferred on each clock cycle. This is directly proportional to the number of wires in the cable
or connectores.
The bandwidth of the bus is calculated by combining the above two measures. Such that:
Bandwidth = width x speed
eg. A 32-bit PCI bus running at 33MHz has a bandwidth of 32 x 33 = 1056Mbit/s (132Mbyte/s)
Note that even though modern motherboards no longer have ISA bus slots within the case, the parallel, serial and PS/2 ports all use this bus and so it is still there.