Scsi Cable Length Restrictions; Table 2. Scsi Bus Length Specifications - Western Digital WD Series Installation Manual

SCSI CABLE LENGTH RESTRICTIONS

Single-ended SCSI drives allow cable lengths of up to 6
meters (19.68 feet). Users who plan to use "Fast" and
"Ultra Fast" data transfers with single-ended models should
follow all the ANSI SCSI guidelines for these operations.
Differential SCSI drives allow cable lengths of up to 25
meters (82.02 feet). Cables must meet the requirements
for differential cables as set forth in the ANSI SCSI
standard.
Drives equipped with a SCA-2 connector are not designed
for direct cable attachment due to the combination of
power and SCSI bus signals.
The ANSI SCSI standard states that any stub from the
main cable must not exceed 0.1 meters (.32 feet) for
single-ended cables and 0.2 meters (.65 feet) for
differential cables.

Table 2. SCSI Bus Length Specifications

Bus Type
SCSI-1
SCSI-2
Fast SCSI-2
Ultra SCSI
All
Property
Maximum bus length
Maximum bus length
Maximum bus length
Maximum bus length
(point-to-point)
Maximum bus length
(multi-drop)
Max. stub length
Min. stub spacing
Single-ended
6m (19.68 ft.)
6m (19.68 ft.)
3m (9.84 ft.)
3m (9.84 ft.)
1.5m (4.92 ft.)
0.1m (.32 ft.)
0.3m (.98 ft.)
!
Differential
25m (82.02 ft.)
25m (82.02 ft.)
25m (82.02 ft.)
25m (82.02 ft.)
25m (82.02 ft.)
0.2m (.65 ft.)
0.3m (.98 ft.)
Released 10/18/96