TC11

This document is an Engineering Change Order Log for the TC11 DECtape Control unit (part of the PDP-11 Family) by Digital Equipment Corporation, covering changes from May 1972 to August 1973.

The log details various modifications, corrections, and problem resolutions:

• Documentation and Physical Changes: Includes updates to effectivity statuses, corrections to assembly drawings and parts lists, and documentation changes for physical component replacements (e.g., a spacer replaced by a latch molding).
• Hardware Configuration & Compatibility: Addresses the transition from the 854 to the 860 Power Control and ensures TC11 cabinets are configured to conform to RK11-C cabinets.
• Functional Bug Fixes: Resolves issues such as the TU56 DECtape drive's 6 AMP fuse blowing under specific conditions (due to TC11 motion commands with duplicate unit numbers) and, most critically, fixes a tape control synchronization problem that could lead to bad block numbers or data read/write errors. The latter fix involves adding logic to ensure multiple sync marks are detected before block marks and is marked as a field retrofit requiring 2 hours of installation and testing.

Overall, the document outlines a series of technical and administrative updates to improve the functionality, compatibility, and documentation of the TC11 DECtape Control.