Why an 18-Bit PDP-K

This document, a technical memorandum from March 1970, proposes the development of the PDP-K, a family of program-compatible computers. The author argues that the PDP-11, due to limitations described in previous memorandums, is insufficient for market requirements. The PDP-K is designed to be implemented as an 18-bit or 36-bit machine in a way that is invisible to the programmer, and it features a more robust instruction set compared to the PDP-11, offering better addressing, indexing, and data handling capabilities to compete with machines like the XDS Sigma 5 and SEL Systems 86.