Configuring the CD-ReWriter

Each peripheral attached to a SCSI-2 host adapter card, as well as the card itself, must be assigned a unique SCSI ID number from 0 to 15 (0 to 7 for SCSI-1). 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.

Each device on the chain, including the host, must be identified by a unique ID number. One SCSI device must not use the same ID number as another, but they may be numbered non-sequentially. Most SCSI host adapters feature external and internal connectors, with the option for the chain to extend in either or both directions. There's no relationship between the IDs and the physical position on the bus, but both ends must be electrically "terminated" with resistors to prevent signal reflections and guarantee data integrity over long cable lengths. Termination comes in several varieties, from physical jumpers or plugs to software configurations.

Here are some general guidelines for SCSI IDs:

• For internal SCSI peripherals, the SCSI ID usually is set by configuring a jumper on the peripheral.
• For external SCSI peripherals, the SCSI ID usually is set with a switch on the back of the peripheral.
• SCSI ID numbers don't have to be sequential, as long as the SCSI host adapter card and each peripheral has a different number. For example, you can have an internal SCSI peripheral with ID 0, and an external SCSI peripheral with ID 6. Gaps in the sequence of numbers don't matter.
• SCSI ID 7 has the highest priority on the SCSI bus. The priority of the remaining IDs, in descending order, is 6 to 0, 15 to 8.
• SCSI host adapter cards are normally preset to SCSI ID 7 and should not be changed. This gives it the highest priority on the SCSI bus.
• Most internal SCSI hard disk drives come from the factory preset to SCSI ID 0.
• If you have 8-bit SCSI peripherals, 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.