Abstract: Circuits for the improved operation of microprogrammable computers are described. This improvement is accomplished by providing a set of read-only memory devices for storing the micro-code for all combinations of arithmetic logic unit function, carry bit and file register address than can be specified by an instruction word executed from Main Memory. In a universal microprogram designed to execute that family of Main Memory instructions that differ only in the functions specified above, the instruction word is used to address the read-only memory devices, the micro-code output of which is used to control the file, carry in bit and arithmetic logic unit. Through the use of these circuits a family of instructions may be executed by a single microprogram and at no increase in execution time over that required for the execution of a microprogram dedicated to a single instruction.

Abstract: A Read-Only Memory device in the CPU of a microprogrammable computer contains a diagnostic program suitable for self-testing the computer. A microprogram for loading this diagnostic program from the Read-Only Memory device into Main Memory is contained in the Control Memory of the CPU. When required, the diagnostic program is loaded into Main Memory and executed thus allowing for the testing of a computer without the need of operational peripherals.