Hardware components of the PC
External PC connection ports
SCSI external ports
A server motherboard will have an on-board host adapter for internal devices, but not provide a SCSI external port for external devices. A host adapter expansion card has both internal and one or more external ports. With the many enhancements to the SCSI standard over the years, a number of different physical connection types are available and some examples are illustrated on the diagram below.
| Old Sun and DG Computers. |  |
| Many 8-bit SCSI FAST (up to 10
Mbytes/sec) computers and host adapters use this 50-pin High-Density connector. |
 |
| Apple/Mac and some older Sun 8-bit workstations. |  |
| All FAST/WIDE 16-bit SCSI-3 computers and host adapters plus old DEC single-ended SCSI use this 68-pin High Density connector. |  |
| New SCA 80-pin. |  |
