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V. Appendix
AP200 Hardware Reference Guide
V. Appendix
SCSI Cable Limits
i. SCSI Cable Limits
SCSI cables have a limit to the length that it may have. Exceeding the length
may cause problems mounting or using any one of the SCSI devices.
Cable Limits Max Data Transfer Rates Max Devices
1) 12m (29.4ft) Ultra2-SCSI (68-pin 80MB/Sec) 15
2) 3m - 1.5m Wide Ultra-SCSI (68-pin 40MB/Sec) 4 - 7
3) 3m (9.8ft) Wide-SCSI (68-pin 20MB/Sec) 15
4) 3m - 1.5m Narrow Ultra-SCSI (50-pin 20MB/Sec) 4 - 7
5) 3m (9.8ft) Narrow Fast-SCSI (50-pin 10MB/Sec) 7
1) A total of 15 “Ultra2-SCSI” devices (ID0-ID15) may be con-
nected to the 68-pin Ultra2 connector on the motherboard.
If connecting Fast/Ultra devices with Ultra2 devices on the
Ultra2 connector, the entire SCSI bus will be limited to the
Ultra SCSI conditions listed above. Mixing SCSI devices is
not recommended.
2) A total of 7 “Wide Ultra-SCSI” devices (ID0-ID15) may be
connected to the 68-pin Wide connector if using a 1.5m (4.9ft)
cable, but only 4 “Wide Ultra-SCSI” devcies if using a 3m
(9.89ft) cable. Ultra-SCSI technology is unstable over long
lengths. Therefore stability will depend on the quality of your
cable and devices.
3) A total of 15 “Wide-SCSI” devices (ID0-ID15) may be con-
nected to the 68-pin Wide connector.
4) A total of 7 “Narrow Ultra-SCSI” devices (ID0-ID6) may be
connected to the 50-pin Narrow connector when using 1.5m
(4.9ft) cable but only 4 devices when using a 3m (9.8ft) cable.
5) A total of 7 “Narrow Fast SCSI” devices (ID0-ID6) may be
connected to the 50-pin Narrow connector.
NOTE
• The SCSI ID for devices on one connector cannot be the same
as the SCSI ID for devices on the other connectors. None of
the devices on any connector can use ID7, which is reserved
for the SCSI controller.
• A maximum of 15 devices may be connected to the mother-
board (three connectors) at one time. The following “Max De-
vices” are for individual connectors and do not take into ac-
count other SCSI devices.
IMPORTANT