ROM checksum testing: Assume a ROM under test is compared to a known-good ROM. If the checksums are different, the ROM under test is ________.

Introduction / Context:
Checksums and hashes detect corruption in stored data and firmware. Comparing a device's checksum to a known-good reference is a fast, practical way to screen for errors during manufacturing or field diagnostics.

Given Data / Assumptions:

• The checksum algorithm is deterministic and covers the entire ROM image.
• Measurement conditions are reliable (no read timing violations causing transient errors).
• We compare against a trusted, correct reference checksum.

Concept / Approach:
If two checksums differ, at least one bit in the covered data differs with overwhelming probability (especially for strong checksums/hashes). While an unstable read could in theory cause a mismatch, in normal conditions a mismatch strongly indicates incorrect contents, hence “very likely to be bad.” Absolute certainty (“definitely bad”) requires ruling out instrumentation errors, but the diagnostic implication is clear.

Step-by-Step Solution:

Verification / Alternative check:
Re-read the ROM, possibly at slower timing; if the mismatch persists, probability of bad contents approaches certainty.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming a simple checksum equals a cryptographic hash; weaker checksums have collision risks, but a mismatch still signals trouble.

Final Answer:
very likely to be bad