RAM diagnostics — interpreting the checkerboard test When a RAM module passes a checkerboard pattern memory test, which conclusion is most appropriate?

Introduction / Context:
Memory diagnostics use test patterns to expose stuck-at and coupling faults. The checkerboard test writes alternating 1s and 0s across memory (e.g., 0xAA and 0x55 patterns), stressing both data lines and cell adjacency. Understanding the meaning of a “pass” helps with quick triage of suspected memory issues.

Given Data / Assumptions:

• Checkerboard patterns: 1010… (0xAA) and 0101… (0x55), sometimes with address variations.
• RAM under test supports both write and read operations.
• Passing indicates correct storage and retrieval of these patterns.

Concept / Approach:
If the module stores both alternating patterns and reads them back without errors, many common failures (stuck-at-0, stuck-at-1, simple coupling) are unlikely. While not an exhaustive proof of perfection, it is a strong positive indicator, hence “probably good.”

Step-by-Step Solution:
Write checkerboard pattern A to all locations; read back and verify.Write inverse checkerboard pattern B; read back and verify.Both verifications succeed → module likely healthy.

Verification / Alternative check:
Additional patterns (walking 1s/0s, address tests, March algorithms) can further validate timing and address/data-line integrity to increase confidence beyond “probably good.”

Why Other Options Are Wrong:

• “Only 1s” or “only 0s”: Passing checkerboard disproves these extremes.
• “Faulty”: Contradicts a clean pass on a stress-inducing pattern.

Common Pitfalls:

• Assuming a single test guarantees perfection; combine multiple patterns for robust assurance.
• Ignoring marginal timing issues that might only appear at temperature or at-speed testing.

Final Answer:
It is probably good.