FCO DMZ32-1001, File corruption on Unibus disk controller drives

This document is a Field Change Order (FCO DMZ32-1001) outlining the need to replace specific M8398 modules to address multiple issues. The primary problem is file corruption on Unibus disk controller drives and users receiving incorrect data due to a "flush bit not clearing DMA correctly," often manifesting as "IMR invalid map register errors" in VAX/VMS systems. Other significant problems include Ultrix and UNIX system hangs/crashes due to SSYNC timeout errors, modem lines failing to reassert DTR after power cycles, system hangs caused by unsupported baud rates, incorrect NXM error reporting, and loss of trailing bits for foreign terminals.

The FCO mandates replacing M8398 modules of Revision E1 or earlier with Revision F1 or later modules. These new modules incorporate updated UBI microcode (version 16) and TIU microcode (version 1C) to resolve the identified bugs. The installation involves powering down the system, swapping the module, and verifying the new microcode with diagnostics. Approximately 10,000 systems are affected, and the estimated installation time is 1.0 hour. The FCO was released on May 18, 1987, with parts becoming available in June 1987.