SCSI capacity planning: how many total devices can share a single narrow SCSI bus (including the host adapter)?

Introduction / Context:
SCSI buses support multiple devices with unique IDs. The allowable count depends on whether the bus is narrow (8-bit) or wide (16-bit). The question targets the classic narrow SCSI case used in many PCs and workstations.

Given Data / Assumptions:

• Narrow SCSI bus (IDs 0 through 7).
• The host adapter itself occupies one ID.
• Correct termination and cabling are assumed.

Concept / Approach:
Narrow SCSI provides 8 IDs total. One is used by the host adapter (often ID 7), leaving up to seven additional devices. Wide SCSI allows 16 IDs (0–15) including the adapter. Because the question does not specify wide SCSI, the standard answer for narrow SCSI is 8 total devices including the controller.

Step-by-Step Solution:

Verification / Alternative check:
Inspect the SCSI BIOS or OS hardware manager to see IDs and verify that the count does not exceed 8 on a narrow bus.

Why Other Options Are Wrong:

• 1: Far below capacity.
• 10 or 20: Exceeds narrow SCSI limits.
• All of the above: Self-contradictory; only one value can be correct.

Common Pitfalls:
Confusing wide SCSI capacities with narrow SCSI and forgetting that the adapter counts toward the total device limit.

Final Answer:
8