Development Team
Motorola did not chronicle the development of the 6800 microprocessor the way that Intel did for their microprocessors. In 2008 the Computer History Museum interviewed four members of the 6800 microprocessor design team. Their recollections can be confirmed and expanded by magazine and journal articles written at the time.
The Motorola microprocessor project began in 1971 with a team composed of designer Tom Bennett, engineering director Jeff LaVell, product marketer Link Young and systems designers Mike Wiles, Gene Schriber and Doug Powell. They were all located in Mesa, Arizona. By the time the project was finished, Bennett had 17 chip designers and layout people working on five chips. LaVell had 15 to 20 system engineers and there was another applications engineering group of similar size.
Tom Bennett had a background in industrial controls and had worked for Victor Comptometer in the 1960s designing the first electronic calculator to use MOS ICs, the Victor 3900. In May 1969 Ted Hoff showed Bennett early diagrams of the Intel 4004 to see if it would meet their calculator needs. Bennett joined Motorola in 1971 to design calculator ICs. He was soon assigned as the chief architect of the microprocessor project that produced the 6800. Others have taken credit for designing the 6800. In September 1975 Robert Cushman, EDN magazine's microprocessor editor, interviewed Chuck Peddle about MOS Technology's new 6502 microprocessor. Cushman then asked "Tom Bennett, master architect of the 6800," to comment about this new competitor. After the 6800 project Bennett worked on automotive applications and Motorola became a major supplier of microprocessors used in automobiles.
Jeff LaVell joined Motorola in 1966 and worked in the computer industry marketing organization. Jeff had previously worked for Collins Radio on their C8500 computer that was built with small scale ECL ICs. In 1971 he led a group that examined the needs of their existing customers such as: Hewlett Packard, National Cash Register, National Data Corporation (CDC), and Digital Equipment Corporation. They would study the customer's products and tried to identify functions that could be implemented in larger integrated circuits at a lower cost. The result of the survey was a family of 15 building bocks; each could be implemented in an integrated circuit. Some of these blocks were implemented in the initial M6800 release and more were added over the next few years. To evaluate the 6800 architecture while the chip was being designed, Jeff's team built an equivalent circuit using 451 small scale TTL ICs on five 10 by 10 inch (25 by 25 cm) circuit boards. Later they reduced this to 114 ICs on one board by using ROMs and MSI logic devices.
John Buchanan was a memory designer at Motorola when Bennett asked him to design a voltage doubler for the 6800. Typical n-channel MOS IC's required three power supplies: -5 volts, +5 volts and +12 volts. The M6800 family was to use only one, +5 volts. It was easy to eliminate the -5 volt supply but the MOS transistors needed a supply of 10 to 12 volts. This on-chip voltage doubler would supply the higher voltage and Buchanan did the circuit design, analysis and layout for the 6800 microprocessor. He received patents on the voltage doubler and the 6800 chip layout. Rod Orgill assisted Buchanan with analyses and 6800 chip layout. Later Orgill would design the MOS Technology 6501 microprocessor that was socket compatible with the 6800.
Bill Lattin joined Motorola in 1969 and his group provided the computer simulation tools for characterizing the new MOS circuits in the 6800. Lattin and Frank Jenkins had both attended UC Berkley and studied computer circuit simulators under Donald Pederson, the designer of the SPICE circuit simulator. Motorola's simulator, MTIME, was an advanced version of the TIME circuit simulator that Jenkins had developed at Berkley. The group published a technical paper, "MOS-device modeling for computer implementation" in 1973 describing a "5-V single-supply n-channel technology" operating at 1 MHz. They could simulate a 50 MOSFET circuit on an IBM 370/165 mainframe computer. In November 1975, Lattin joined Intel to work on their next generation microprocessor.
Bill Mensch joined Motorola in 1971 after graduating from the University of Arizona. He had worked several years as an electronics technician before earning his BSEE degree. The first year at Motorola was a series of three month rotations through four different areas. Mensch did a flowchart for a modem that would become the 6860. He also worked the application group that was defining the M6800 system. After this training year, he was assigned to the 6820 Peripheral Interface Adapter (PIA) development team. Mensch was a major contributor to the design of this chip and received a patent on the IC layout and was named as a co-inventor of seven other M6800 system patents. Later Mensch would design the MOS Technology 6502 microprocessor.
Mike Wiles was a design engineer in Jeff LaVell's group and made numerous customer visits with Tom Bennett during 6800 product definition phase. He is listed as an inventor on eighteen 6800 patents but is best known for a computer program, MIKBUG. This was a rudimentary BIOS for a 6800 computer system that allowed the user to examine the contents of RAM and to save or load programs to tape. This 512 byte program occupied half of an MCM6830 ROM. This ROM was used in the Motorola MEK6800 design evaluation kit and early hobby computer kits. Wiles stayed with Motorola, moved to Austin and helped design the MC6801 microcontroller that was released in 1978.
Chuck Peddle joined the design team in 1973 after the 6800 processor design was done but he contributed to overall system design and to several peripheral chips, particularly the 6820 (PIA) parallel interface. Peddle is listed as an inventor on sixteen Motorola patents, most have six or more co-inventors. Like the other engineers on the team, Peddle visited potential customers and solicited their feedback. Peddle and John Buchanan built one of the earliest 6800 demonstration boards. In August 1974 Chuck Peddle left Motorola and joined a small semiconductor company in Pennsylvania, MOS Technology. There he led the team that designed the 6500 microprocessor family.
Read more about this topic: Motorola 6800
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