Asus AP2500 Hardware Reference Manual - Page 36

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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.

CAUTION:

Exceeding the SCSI cable limits may cause unreliable data

transfers even if all the devices are mounted properly.

NOTES:

•

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. The following "Max Devices" are for individual

connectors and do not take into account other SCSI devices.

Cable Limits

1) 12m (29.4ft)

2) 3m - 1.5m

3) 3m (9.8ft)

4) 3m - 1.5m

5) 3m (9.8ft)

Notes for the above chart:

1) A total of 15 "Ultra2-SCSI" devices (ID0-ID15) may be connected to the

68-pin Ultra2 connector on the motherboard.

NOTE: 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.

2) A total of 8 "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" devices if using a 3m (9.89ft) cable. Ultra-SCSI technology

is unstable over long lenghts, therefore stability will depend on they qual-

ity of your cable and devices.

3) A total of 15 "Wide-SCSI" devices (ID0-ID15) may be connected 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 3m (9.8ft) cable. Ultra-SCSI technology is un-

stable over long lengths, therefore stability will depend on the quality of

your cable and devices.

5) A total of 7 "Narrow Fast SCSI" devices (ID0-ID7) may be connected

to the 50-pin Narrow connector.

III. Appendix

Max Data Transfer Rates

Ultra2-SCSI (68 pin 80MB/Sec)

Wide Ultra-SCSI (68 pin 40MB/Sec)

Wide-SCSI (68 pin 20MB/Sec)

Narrow Ultra-SCSI (50 pin 20MB/Sec) 4 - 7

Narrow Fast-SCSI (50 pin 10MB/Sec) 7

AP2500 Hardware Reference Guide

Max Devices

4 - 8