What's the "een" in Halloween?
(MC14500B) A 1-bit ICU from Motorola. Probably the limit in small processors, the 14500B had a 4-bit instruction and controlled a single data read/write line, used for application control. It had no address bus - that was an external unit that was added on. Another CPU could be used to feed control instructions to the 14500B in an application. It had only 16 pins, less than a typical RAM chip, and ran at 1 MHz.