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AP3000 Hardware Reference Guide 39
V. Appendix
V. Appendix
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 - 8
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
SCSI Cable Limits
Exceeding the SCSI cable limits may cause unreliable data trans-
fers even if all the devices are mounted properly.
CAUTION
IMPORTANT
• Narrow refers to 50 pin and Wide refers to 68 pin. Don’t get
confused by the width of the connector or cable.
• 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 motherboard
(three connectors) at one time.
NOTE
• A total of 15 “Ultra2-SCSI” devices (ID0-ID15) may be connected
to the 68-pin Ultra2 connector on the motherboard.
• If connecting Fast/Ultra devices with Ultra2 devices on the Ul-
tra2 connector, the entire SCSI bus will be limited to the Ultra
SCSI conditions listed above. Mixing SCSI devices is highly
not recommended.
• A total of 8 “Wide Ultra-SCSI” devices (ID0-ID15) may be con-
nected to the 68-pin Wide connector if using a 1.5m (4.9ft) cable,
but only 4 “Wide Ultra-SCSI” devices if using a 3m (9.89ft) cable.
Ultra-SCSI technology is unstable over long lenghts, therefore sta-
bility will depend on they quality of your cable and devices.
• A total of 15 “Wide-SCSI” devices (ID0-ID15) may be connected
to the 68-pin Wide connector.
• 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 3m (9.8ft) cable.
Ultra-SCSI technology is unstable over long lengths, therefore
stability will depend on the quality of your cable and devices.
• A total of 7 “Narrow Fast SCSI” devices (ID0-ID7) may be con-
nected to the 50-pin Narrow connector.