B.S.T.J. brief: MAC-4: A single-chip microcomputer

MAC-4 is a single-chip microcomputer designed to fill a rising need in many Bell System applications. Its instruction set promotes program memory efficiency and emphasizes bit manipulation, MAC-4 is implemented in CMOS technology, resulting in a low power dissipation which can be further reduced by using a special halt instruction. These features make it valuable as a controller in a telephone environment and for telephone loop power applications. Figure 1 is a photograph of the MAC-4 chip.