PDP-1 Supplement

This document serves as a technical supplement for the PDP-1D-45 computer system. It outlines specific custom instructions and configurations implemented at Bolt Beranek and Newman. Key sections include:

• Memory Reference Instructions: Details on Load Character (LCH), Deposit Character (DCH), and Two's Complement Add (TAD).
• The Skip Group: Instructions for testing I/O register states.
• The Special Operate Group: Describes microprogram instructions, including the "ring mode" for memory looping and various flag operations.
• In/Out Transfer Group: Comprehensive details on I/O instructions for the Type 23 Drum, Data Communication System Type 630, and the Precision CRT Display 30.