FCO 9XXX-0011, ALPHA particle effects causing intermittent errors

This Field Change Order (FCO 9XXX-0011) addresses critical issues in VAX 9XXX systems equipped with Vector Accelerator CPU Options, specifically intermittent errors, incorrect results, and non-recoverable data parity errors. These anomalies are caused by ALPHA particle effects that are difficult to diagnose. The solution mandates retrofitting all affected VAX9000 systems by replacing the P1018-AA Multi Chip Unit (MCU) at or below revision "F" with revision "H" (as per ECO #P1018-A-MR002). This upgrade enhances circuit stability through a dual feedback latch, mitigating the effects of alpha particles. The FCO also requires updating all field spares to the new revision. The installation procedure, which includes system shutdown, MCU replacement, and diagnostic testing, is estimated to take approximately 4.0 hours for a UNI CPU configuration.