A concurrent microprogramming facility

Control-unit microcode is characterized by the control of multiple asynchronous devices. This paper describes the Concurrent Microprogramming Facility (CMF), a general-purpose microcode operating system that applies recent advances in programming technology to define a uniform method of expressing this inherent asynchrony. This method is shown to be the basis for the partition of the microcode function and to provide a framework for communication between programmers as well as programs. CMF provides an environment where microcode is viewed as disjoint asynchronous processes that communicate with each other and hardware adapters using a small set of primitives based on the concept of message passing. A uniform process interface both streamlines documentation and accommodates multiprocessor designs. A macro-based system definition facility drives the system and allows the structure of a large microprogram to be specified on a single page.