Maximum Cable Lengths - Adaptec 1821900 Reference

The following example shows two Ultra160/Ultra2 SCSI devices
connected to the external connector. As in the previous diagrams,
the last device on the SCSI bus must use an LVD/SE terminator plug
in order to operate at its maximum speed.
T
Terminated
device

Maximum Cable Lengths

The total length of cabling (internal and external) on the SCSI bus
cannot exceed the maximum lengths listed in the following table.
The third column lists the maximum number of SCSI devices you
can connect to the SCSI card.
Maximum
Cable Length Data Transfer Rate
25 m (82.0 ft) Ultra160 SCSI (160 MBytes/sec)
and Ultra2 SCSI (80 MBytes/sec)
12 m (39.4 ft) Ultra160 SCSI (160 MBytes/sec)
and Ultra2 SCSI (80 MBytes/sec)
3 m (9.8 ft) Fast Wide SCSI
(20 MBytes/sec)
3 m (9.8 ft) Fast SCSI
(10 MBytes/sec)
3 m (9.8 ft) Ultra SCSI
(40 MBytes/sec for 16-bit,
20 MBytes/sec for 8-bit)
1.5 m (4.9 ft) Ultra SCSI
(40 MBytes/sec for 16-bit,
20 MBytes/sec for 8-bit)
1
Mixing Fast/Ultra devices with Ultra160 and Ultra2 SCSI devices causes the entire
SCSI bus to default to Ultra SCSI speeds and cable length requirements.
2
Ultra SCSI data transfer rates do not currently support more than seven devices
connected to the SCSI card.
Connecting SCSI Devices
Maximum Devices
Supported
1
1
15
15
7
4
2
5-7
25