Comments on lack of HALT instruction

This technical memorandum discusses the problem caused by the PDP-X computer's lack of a HALT instruction, which is typically the first instruction checked by diagnostic programs to indicate error conditions. The proposed alternative, a "B ." (jump to current program counter) instruction, is deemed more complicated than HALT because it requires a functional memory system, making it unsuitable for the initial diagnostic check. The document suggests that if "B ." is used, the computer console should automatically display the instruction register and program counter, and allow viewing of memory or general purpose register contents during its execution. It also outlines alternative restart procedures (external interrupt or STOP/START at a specified location) to replace the HALT and CONTINUE functions. Finally, it recommends that the START function should not clear the PI system or accumulators, and that the I/O RESET and START functions should be controlled by separate console switches.