G109

This document is an Engineering Change Order (ECO) Log for the G109 Control And Data Loops module, used in PDP-11 and PDP-15 processor systems. It details various problems identified and their corresponding corrections from August 1972 to March 1973.

The ECOs address a range of issues including:

• Hardware and Mechanical: Fixing loose standoffs by switching to drilled, screw-mounted ones.

• Electrical and Performance:

  • Correcting critical timing issues such as the memory system's cycle time being too short (requiring replacement of delay lines), early assertion of SLAVE SYNC, and premature write switch activation.
  • Optimizing threshold circuits and correcting resistor values to prevent stack failures.
  • Replacing slow or incorrect integrated circuit components.
  • Resolving issues with STROBE flip-flop clearing.

• Manufacturing and Quality: Ensuring proper wiring for ground jumpers to prevent shorts, and allowing component substitution to mitigate parts shortages.

• Documentation and Revision Control: Updating G109 board etch revisions, correcting circuit schematics to reflect different versions (e.g., G109-YA), and managing field service concerns regarding revision letter consistency on modules and handles.

Many entries specify "in-plant" and "field" effectivity, often requiring rework on existing modules or applying changes to new production based on specific etch revisions.