JMS Y - Interrupt Test

This document describes the "JMS Y - Interrupt Test," a diagnostic program for the PDP-9 computer. Its main objective is to determine if the PDP-9 can complete a "JMS Y" instruction before a program interrupt occurs.

The test works by setting an I/O flag and then transferring control to a randomly placed ION/JMS Y instruction group in memory. The system is expected to execute the JMS Y instruction completely before the program enters an interrupt state. If no error is detected, the instruction group is moved to another random memory location, and the test is repeated. Errors are communicated to the operator through the Teletype or by causing program halts.

The program requires a standard PDP-9 computer and utilizes all 8K of its memory. The program itself occupies memory locations 17400 to 17771, while testing all locations below 17377. Loading involves using an HRI tape and setting ADDRESS SWITCHES to 17400. Starting the program requires specific ACCUMULATOR SWITCH settings to control behavior such as halting on errors, printing messages, or looping, followed by an I/O RESET and START. The document also details error recovery procedures for both program-diagnosed errors and interrupt failures, which typically involve resetting switches and restarting the program. The internal description outlines steps like initialization, random generation of instruction and data addresses, filling the test memory area with HALT instructions, and verifying memory contents after returning from a program interrupt.