MS630 Memory Problem Determination/Resolution Guide

This document, EK-MS630-FI-001, is a Memory Problem Determination/Resolution Guide for MS630 memory arrays used in MicroVAX II based systems, published by Digital Equipment Corporation in June 1991.

Its primary objective is to define the recommended maintenance strategy for these memory arrays, emphasizing problem determination (identifying the underlying cause) and guiding the user on when to replace Field Replaceable Units (FRUs). It does not introduce new procedures but elaborates on existing ones.

The guide instructs users to start by identifying the specific problem symptom from a priority-ordered list. It then categorizes memory faults into four main types, each with a different recommended action:

1. Hard Fault (Theory Number 1): A reproducible fault, typically due to a physical component failure (e.g., MDM diagnostics fail, VMS maps bad pages, POST fails, system won't boot). Action: Replace the failed FRU.
2. Transient Fault (Theory Number 2): An isolated, one-time parity error (often caused by an alpha particle). Action: No FRU replacement required; record the event.
3. Multiple Symptom Fault (Theory Number 3): Occurs when there is more than one problem symptom or multiple FRUs have failed. These are complex and may point to common component failures (e.g., cable, CPU module). Action: Requires additional manual diagnosis or contacting support.
4. Intermittent Fault (Theory Number 4): A recurring but not easily reproducible fault, likely due to a marginal physical component (e.g., periodic system crashes due to parity errors, MDM diagnostics probably don't fail). Action: Replace the failed FRU.

The document also provides detailed FRU replacement procedures (identifying, replacing with a compatible spare, verifying system functionality) and guidelines for tagging replaced FRUs with information on the fault type (hard/intermittent) and diagnosis method for tracking and repair. It assumes the user has service knowledge of the MicroVAX system.