Asus LS99 - Manual (Page 27)

Appendix 27
Appendix A
SCSI (pronounced “scuzzy”) stands for Small Computer Systems Interface. SCSI is
an industry standard computer interface for connecting SCSI devices (such as a hard
disk drive, CD-ROM drive, or scanner) to a common SCSI bus. A SCSI bus is an
electrical pathway that consists of a SCSI adapter card (such as the ASUS LS99
SCSI Card) installed in a computer and one or more SCSI devices. SCSI cables are
used to connect the devices to the SCSI adapter card. The ASUS LS99 SCSI Card
has two independent SCSI buses (channels).
For the SCSI bus to function properly, a unique SCSI ID must be assigned to the
SCSI card and each SCSI device connected to it, and the SCSI bus must be properly
terminated.
SCSI IDs
Each device attached to the ASUS LS99 SCSI Card, as well as the ASUS LS99
SCSI Card itself, must be assigned a unique SCSI ID number from 0 to 15 for each
of the two SCSI buses. A SCSI ID uniquely identifies each SCSI device on the SCSI
bus and determines priority when two or more devices are trying to use the SCSI bus
at the same time.
Refer to the device’s documentation to set the SCSI ID. Here are some general
guidelines for SCSI IDs:
• For internal SCSI devices, the SCSI ID usually is set by configuring a jumper on
the device.
• For external SCSI devices, the SCSI ID usually is set with a switch on the back
of the device.
• SCSI ID numbers do not need to be sequential, as long as the ASUS LS99 SCSI
Card and each device has a different number. For example, on each of the two
SCSI buses you can have an internal SCSI device with ID 0, and an external
SCSI device with ID 6.
• SCSI ID 7 has the highest priority on the SCSI bus. The priority of the remaining
IDs, in descending order, is 6 to 0, then 15 to 8.
• On both SCSI buses (channels) the ASUS LS99 SCSI Card is preset to SCSI ID
7 and should not be changed. This gives the card the highest priority on the SCSI
bus.
• Most internal SCSI hard disk drives come from the factory pre-set to SCSI ID 0.
• If you have 8-bit (or Narrow) SCSI devices, they must use SCSI IDs 0, 1, 2, 3, 4,
5, or 6. SCSI ID 0 is recommended for the first SCSI hard disk drive.
A
Understanding SCSI