When installing a SCSI CD-ROM drive on an existing SCSI bus, what should the SCSI ID of the new CD-ROM be set to for correct operation?

Introduction / Context:
SCSI (Small Computer System Interface) devices share a common bus where each device must have a unique SCSI ID to avoid contention. Properly assigning the SCSI ID when adding a CD-ROM ensures the host adapter can enumerate all devices without conflicts.

Given Data / Assumptions:

• There is an existing SCSI bus with other devices present.
• Standard SCSI ID ranges apply (e.g., 0–7 on narrow SCSI, where the host adapter often uses a reserved ID like 7).
• Termination rules are followed at the physical ends of the bus.

Concept / Approach:
On a SCSI chain, every device (including the host adapter) must have a unique ID. The CD-ROM's SCSI ID must not duplicate any existing ID. Many systems reserve specific IDs (e.g., ID 7 for the host, ID 0 for the boot hard disk), but the universal requirement is uniqueness, not a fixed number for optical drives.

Step-by-Step Solution:

Verification / Alternative check:
If the adapter BIOS or OS detects two devices with the same ID, the bus will exhibit errors or one device will be missing. After assigning a unique ID, both devices appear and function normally, confirming the rule.

Why Other Options Are Wrong:

• B0007: Not a valid SCSI ID format; IDs are numeric within the bus range.
• The same address as the SCSI device before the CD-ROM: Causes ID conflict and enumeration failure.
• SCSI ID = 1: Arbitrary; may already be in use. Uniqueness matters, not a specific number.
• None of the above: Incorrect because the correct action is to use an unused SCSI address.

Common Pitfalls:
Forgetting to adjust termination when inserting a new middle device, assuming the optical drive must be ID 1, and overlooking that the host adapter often occupies ID 7 on narrow SCSI.

Final Answer:
An unused SCSI address