Power-up self test writes in one location in NVRAM

This document (KN220-0001) describes a Field Change Order (FCO) for DECsystem 5500 units equipped with Revision D or E M7637-AA CPU modules. The issue involves the power-up self-test writing to an NVRAM location that causes data corruption if a power failure occurs before the NVRAM data is written back to the disk. The solution requires either upgrading to Revision F04 modules or installing new EPROMs for Revision E modules. The document provides detailed rework instructions, including identification of the module revision, procedures for EPROM installation, handling of the Prestoserve battery backup, and administrative reporting requirements.