The IBM RT PC ROMP processor and memory management unit architecture

The ROMP processor is the microprocessor used in the IBM RT PC. It is a 32-bit processor with an associated memory management unit implemented on two chips. ROMP is derived from the pioneering RISC project, the 801 Minicomputer at IBM Research. This paper describes some of the trade-offs which were made to turn the research project into a product. It gives an introduction to the architecture of ROMP, including the addressing model supported by ROMP's memory management unit. Some of the unique features of the programming model are explained, with high-level language coding examples which show how they can be exploited. ROMP's architecture is extensible, and the fact that almost all programming for the RT PC has been in high-level languages means that the RT PC hardware architecture can be extended as needed to meet future requirements while preserving the investment in existing software.