TheLSI-11/23 Control Store Microarchitecture

The LSI-11/23, an LSI version of Digital Equipment's PDP-11/34, is the first microcomputer with the performance and features of a midrange minicomputer. Three forty-pin packages containing five NMOS LSI chips form the basis for a complete CPU on an 5" x 8" board with extensive memory management features and both single and double precision floating point instructions (see Figure 1) . This paper describes one of the features, the control store and control sequencer*, that enabled the LSI-11/23 to obtain two and a half times the performance of the LSI/11, while maintaining a flexible microarchitecture for instruction set extensions.