SCSI device IDs and jumpers: On a 3-bit SCSI ID jumper block where 1 = shorted and 0 = open, how is logical ID 3 represented?

Introduction / Context:
Legacy SCSI devices use jumper blocks or DIP switches to set the device ID. Understanding binary representation of IDs ensures unique addressing on the bus and prevents conflicts during configuration.

Given Data / Assumptions:

• Three jumpers encode the SCSI ID in binary.
• Convention: jumper installed = 1, jumper removed = 0.
• Logical ID requested is 3.

Concept / Approach:

Binary representation maps directly to jumper states. With three bits (usually representing 1, 2, 4), the value 3 equals 1 + 2, so the least significant two bits are set to 1 and the highest bit is 0. Therefore the pattern is 011.

Step-by-Step Solution:

Verification / Alternative check:

Device documentation or silk-screening often labels the pins with their weights (1, 2, 4). Installing jumpers on 1 and 2 yields ID 3. The host adapter utility lists the device at ID 3 during bus scan.

Why Other Options Are Wrong:

• 100: Equals decimal 4, not 3.
• 010: Equals decimal 2, not 3.
• . 101: Equals decimal 5, punctuation is also erroneous.
• None of the above: Incorrect since 011 is correct.

Common Pitfalls:

Reading bit order backwards; forgetting termination rules at bus ends; duplicate IDs causing devices to vanish or the bus to hang.

Final Answer:

011