PDP-7 Extended Checkerboard

The PDP-7 Extended Checkerboard is a diagnostic program designed to verify the performance of 4096 to 32,768 words of core memory and its associated logic on a PDP-7 computer. It systematically tests memory in 4096-word increments using four distinct patterns and their complements to ensure thorough, worst-case testing. The program itself resides in the lower addresses of the first 4K of memory and relocates to test that region effectively.

The document provides detailed instructions for loading the binary tape in HRI mode and configuring the test using AC and Address switches. Users can specify whether to test extended memory, specific 8K memory areas, or prevent program relocation by adjusting these switches. It outlines various error halts (HALT 1, 2, 3) indicating issues like bit errors, failed registers, or control word discrepancies, along with instructions for recovery. Key restrictions include the requirement for the EXTEND mode switch to be down when loading the program outside the first 8K of memory, and it recommends running the Maindec 703 Memory Address Test beforehand. The program takes approximately 53 seconds to test each 4096-word segment of memory.