Bus Length - Sun Microsystems Enterprise 250 Owner's Manual

The addresses for the internal CD-ROM and tape drives are determined by jumpers
located on the drives. If the CD-ROM and tape drives have been factory-installed,
they are configured with the correct addresses for the system.
When installing an internal CD-ROM or tape drive as an option, you should verify
the address settings on these devices. The settings usually involve three sets of pins
that determine the address in binary. Attaching a jumper across a set of pins creates
a binary 1 in that position.
TABLE 5–5
See the documentation accompanying the drive for device-specific information about
checking and setting jumpers.

Bus Length

For UltraSCSI performance on the external SCSI bus, you must adhere to the
following bus length restrictions for daisy-chained SCSI devices:
4 For 1 to 3 devices, the maximum bus length is 3 meters (9.84 feet)
4 For 4 to 7 devices, the maximum bus length is 1.5 meters (4.92 feet)
You must include the Enterprise 250 internal bus length (0.5 meter/1.7 feet) in your
bus length calculations.
If you exceed these bus length restrictions, UltraSCSI devices may operate at less
than 40 Mbytes/sec. Under such conditions, an UltraSCSI device may experience
errors that eventually cause it to reset and operate at 20 Mbytes/sec.
For Fast/Wide performance on the external SCSI bus, the maximum SCSI bus length
for daisy-chained SCSI devices is 6 meters (19.7 feet), including the Enterprise 250
internal bus length (0.5 meter/1.7 feet).
Sun Enterprise 250 Server Owner's Guide ♦ Revision A, June 1998
96
000 = SCSI
2
ID 0
011 = SCSI
2
ID 3
110 = SCSI
2
ID 6
001 = SCSI
2
ID 1
100 = SCSI
2
ID 4
111 = SCSI
2
ID 7
010 = SCSI
2
ID 2
101 = SCSI
2
ID 5