Disk Control

This document is an Engineering Change Order (ECO) log for the M7255 Disk Control module, used in PDP-11 and PDP-15 systems. It lists various engineering changes (M7255-00001 through M7255-B0007) spanning from 1972 to 1974. The log details specific problems identified in module designs, such as etch errors, timing issues, interrupt polling logic faults, power fail sequence damage risks, and noise susceptibility due to poor power and ground distribution. Each entry provides a problem description, the required correction (often involving board rework or component replacement), and instructions regarding in-plant and field effectivity.