1974 · Microprocessor Prototype Board · Work 888 of 1,871
A development laboratory near Phoenix in Arizona, a hand in a short white shirt sleeve lifting a grey-green plug-in circuit card from a card frame by its loop of white cloth tape, the card seventeen centimetres long with gold contact fingers along one edge and a field of fine holes, on it five chips in coloured sockets, a white ceramic chip with a small gold plate in a turquoise socket, the largest a dark grey chip with a blank cream paper tag in a red-brown socket, another in a blue socket, every chip plain smooth and unmarked, short white wire links, through slatted blinds bright desert light and a tall saguaro cactus.
What it was used for
A prototype board of the Motorola M6800. The Computer History Museum describes object 102711296 briefly as "a Motorola 6800 prototype board (1974)", 5 by 1 by 6 1/2 inches, gift of Thomas H. Bennett (per The Chip Letter the 6800's chief architect), and lists as part numbers MPU XC 6800, RAM XC 6810 and PIA XC 6829. On the course of development The Chip Letter says: layout of the design began at the end of 1972, the first working parts arrived in February 1974 with bugs in a few instructions, the chip was announced in March 1974, and full production began only in November 1974. Bennett's team numbered about 17.
What was new
What the 6800 could do that rivals could not: run on a single 5 V supply where others needed 5, -5 and 12 V (The Chip Letter). Plus 2 accumulators of 8 bits and a 16-bit index register; loading an 8-bit constant took 2 cycles against 7 on the 8080, while the 6800 lacked the 16-bit addition the 8080 had. A Motorola advertisement of April 1975 quoted by The Chip Letter calls the M6800 family - memories, the 6820 parallel part, the 6850 serial part, the 6860 modem part - the first LSI family designed as a coherent set of building blocks; that is advertising language. The control logic was first planned as a PLA, proved too slow, and was replaced by ROM decoding with a state counter.
What the sources leave open: The museum record says nothing about how the board was used and names no team, so no purpose is asserted here. The part number PIA XC 6829 is as given in the catalogue; The Chip Letter lists the family's parallel part as the 6820. Neither source says whether these are the same part.