FCO 85XBA-1008, MS88-DAs on VAX 85x0 systems

This Field Change Order (FCO 85XBA-1008) addresses a critical memory fault isolation problem in VAX 85X0 systems that utilize MS88-DA memory. The existing Memory Control Logic (MCL) module (F1001) is unable to reliably isolate intermittent 64 meg memory array problems down to the failing daughter board (FRU), often only identifying the issue at the mother board level.

The FCO mandates an upgrade to resolve this by replacing the F1001 MCL module with the F1021 Memory Control Board (Rev. B1/2/3/4/5). The installation procedure, estimated to take 1.0 hour for each of the 452 affected systems, involves a complete system shutdown, taking ESD precautions, physically swapping the F1001 module for the F1021, and then powering on the system to run extensive diagnostic tests to verify CPU operation and memory integrity. Post-installation, the Site Management Guide must be updated, and the FCO activity reported.