SCSI cables are the interconnecting cables used to provide the SCSI interface to the internal and external drives. To ensure error-free data transfer, the SCSI cables should comply with the relevant recommendations.
The internal hard disk drives are connected via ribbon cables; round cables are available for connecting external drives.
In accordance with the operating modes of SCSI, which supports the transmission of single-ended and balanced differential signals, SCSI cables are multi-shielded, unshielded and with twisted pairs. The latter are used for the LVD bus.
In the case of the ribbon cable, there is a ground wire between each two signal-carrying wires to protect against crosstalk.
SCSI cables are 50-, 68-, 80-, or 110- pin, with the 110-pin cable first defined in SCSI-3. Pin 1 is marked red on the flat cable. The impedance of SCSI cables ranges from 90 ohms to 140 ohms and have cable lengths that depend on the SCSI version, and are 1.2 m, 3 m, 13 m, and 25 m.