Setting SCSI IDs
A simple SCSI chain works like a network, and-like a network-each device requires its own unique address. But unlike a network, setting an address on a SCSI chain is simple. A SCSI device can have any ID number in a range recognized by the host adapter, as long as no other device on the same chain has been set to the same number.
In SCSI numbering conventions:
- The host adapter is typically set to SCSI ID 7. (This is a de facto standard, not a requirement.)
- There is no mandated order for the use of SCSI IDs, but the SCAM feature will use a preestablished pattern of IDs if one is available.
- The ID of a bootable hard disk drive may be preset by the host adapter manufacturer. Most manufacturers use SCSI ID 0, although a few are configured to SCSI ID 6.
Setting a SCSI ID for a device is accomplished using jumpers or switches located on, or inside, the SCSI device. Typically, all internal SCSI hard disk drives use jumpers to set their IDs. External devices usually (but not always) have switches. Some SCSI devices have automatic ID and termination, using SCAM.
CAUTION
Some external devices will offer a limited number of choices. This lack of choices could cause some problems when the chain is full. You might then have to adjust other drive IDs in order to find a unique ID for the new drive.
If you plan to utilize a SCSI drive as your C drive (this is required if you want to boot into MS-DOS from this drive), it must be configured as a bootable drive. This is done by either specifying the host adapter as the "bootable" SCSI ID or setting the host adapter to emulate a standard AT-style controller.