External Scsi Expansion - Compaq AlphaServer DS20E Reference Manual

5.13 External SCSI Expansion

External SCSI devices, such as tabletop or rackmounted storage
devices, can be connected to the system using PCI-based SCSI adapters.
SCSI Expansion Rules
Observe the following rules to determine if a particular device can be used:
•
The device must be supported by the operating system. Consult the
software product description for the device or contact the hardware vendor.
•
A maximum of 14 devices can be attached to any one wide SCSI channel.
•
Each device on the bus must have a unique SCSI ID. You may need to
change a device's default SCSI ID to make it unique. For information about
setting a device's ID, refer to the guide for that device.
•
The entire SCSI bus length, from terminator to terminator, must not exceed
6 meters for fast-differential connection to SCSI or 3 meters for fast single-
ended connection.
•
Ensure that the SCSI bus is properly terminated and that no devices in the
middle of the bus are terminated.
•
For best performance, wide devices should be operated in wide SCSI mode.
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