M-1124 RdrPunTest Aug61

This permanent memorandum, dated August 29, 1961, describes a utility program designed for PDP-1 Maintenance Personnel to test the performance of the PDP-1 paper tape reader and punch.

The reader test involves reading a closed-loop tape of alternating ones and zeroes. As each bit is read, it is checked against values stored in core memory. The timing between read commands and the selection of bits being tested can be adjusted using Test Word (TW) switches.

The punch test punches alternate ones and zeroes from a buffer area in memory onto a new tape. A key feature is that this newly punched tape can then be fed back into the reader and verified using the reader test function, creating a comprehensive closed-loop test for the punch.

The document provides detailed operating instructions for both tests, including steps to load the program, set console switches (e.g., SS #1, test address switches, TW switches 0-17) to control parameters like timing and buffer size. Error conditions result in the computer halting, with error details visible in the Accumulator (AC) and the last word read in the Input/Output (IO) register. Maintenance personnel are also advised to vary hardware voltage margins during testing to diagnose performance issues.

The memorandum concludes with the assembly language code for the program and instructions for generating the specific closed-loop test tape required for the reader test.