In January 1981 the chip designers at MOS Technology had nothing to do. “We were fresh out of ideas for whatever chips the rest of the world might want us to do,” their manager, Albert Charpentier, remembered. “So we decided to produce state-of-the-art video and sound chips for the world’s next great video game.” Nine months later the chips worked, and a year after that they were inside the Commodore 64. IEEE Spectrum called Charpentier the machine’s chief designer.
The VIC chip
Charpentier ran the LSI group at MOS, the part of Commodore’s semiconductor business that designed large-scale integrated circuits. Commodore Magazine gave his title as “Design Manager”. Michael Tomczyk, Jack Tramiel’s assistant, described him as “a likable shirtsleeves manager” who “was in charge of chip design”, and elsewhere as “a brilliant engineering manager”.
His first well-known chip was the VIC, the Video Interface Chip. Tim Danton’s history says Charpentier began it in late 1976, soon after Commodore bought MOS, as a video chip for games machines, and that MOS offered it to other manufacturers without finding a customer. Its screen was only 22 characters wide, and next to the PET’s 40 columns it looked like a toy.
The chip found a use through one of Charpentier’s recruits. He hired Bob Yannes in 1979, and Yannes built a prototype computer around the VIC to show that it could make a cheap colour machine. When Tramiel asked for exactly that, Tomczyk wrote, the president of MOS “volunteered his semiconductor design engineers, including a young chip designer named Bob Yannes, who was programming the VIC chip, and a brilliant engineering manager named Al Charpentier.” The result was the VIC-20. IEEE Spectrum credited the LSI group under Charpentier with “some of the chips that went into Commodore’s VIC-20”.
The VIC-II and the Commodore 64
The 1981 project began with homework. The team looked at the machines they would compete with: the Mattel Intellivision, the Texas Instruments 99/4A and the Atari 800. From those they took the ideas they liked, which IEEE Spectrum listed as “sprites from the TI machine, collision-detection techniques and character-mapped graphics from the Intellivision, and a bit map from their own VIC-20.” The new graphics chip, the VIC-II, showed 40 columns of text, bitmaps, 16 colours and eight hardware sprites, and could interrupt the processor at a chosen line of the screen. Yannes designed the sound chip, the SID, alongside it.
Charpentier’s brief was generous. “Al was given the freedom, within a certain die size, to put in everything he could, working backward within the size we planned,” a colleague told IEEE Spectrum. Charles Winterble, Commodore’s director of engineering, gave the project its go-ahead. The first chips came back from the fab working “except for one bad sprite.”
In late 1981 Tramiel decided to put the chips into a home computer with 64K of RAM. At the time, 64K memory chips were expensive, and Charpentier explained the reasoning: “Jack made the bet that by the time we were ready to produce a product, 64K Rams would be cheap enough for us to use.” To save time, the team reused the VIC-20’s case. The engineers drew up the machine’s architecture in two days and had five working prototypes by the new year, in time for the Winter Consumer Electronics Show in January 1982.
Problems they could not fix
Charpentier was frank about the machine’s faults. Its most notorious early defect was “sparkle”, specks of light on the screen. It took the engineers three weeks to trace it to a ROM that mistook a brief voltage spike on the bus for a valid address.
The disk drive was worse. “The disk drive? What a gory story!” he said. Commodore’s serial bus had been designed for the VIC-20, and its PET drives had used a parallel IEEE-488 bus. The team fixed the fault in the serial shift register of the 6526 chip, “but we couldn’t use it, because the disk drive had to be compatible.” So the C64 talks to its 1541 drive one bit at a time under software control, which is why it is so slow, and why so many programs brought their own fast loaders.
Ensoniq
Charpentier looked back on the C64 project as a lucky moment in the company’s history: “The freedom that allowed us to do the C-64 project will probably never exist again.” In the spring of 1983 he left Commodore with Yannes, Winterble and two engineers who had helped bring the machine into production, David Ziembicki and Bruce Crockett. They formed a company called Peripheral Visions, which became Ensoniq. When IEEE Spectrum wrote its account in 1985, Charpentier was Ensoniq’s vice-president of engineering and the company was about to release its first product, a music synthesiser. That was the Mirage sampling keyboard, which Compute! reported at $1,700 in January 1985.
Sources
- Tekla S. Perry and Paul Wallich, “Design case history: the Commodore 64”, IEEE Spectrum, vol. 22 no. 3, March 1985 (read in the version republished at spectrum.ieee.org): Charpentier as head of the LSI group and chief designer of the C64; the VIC-20 chips; “fresh out of ideas”; Winterble’s go-ahead; the machines examined and the ideas borrowed; the die-size freedom; “one bad sprite”; the 64K RAM bet; the two-day architecture and five prototypes; the VIC-20 case; sparkle; the disk drive and the 6526; “will probably never exist again”; Peripheral Visions, Ensoniq and his post there.
- Commodore Magazine, vol. 3 no. 2, April 1982, p. 104: “Unsung Heroes”, naming “Design Manager Al Charpentier”.
- Michael S. Tomczyk, The Home Computer Wars: An Insider’s Account of Commodore and Jack Tramiel (Compute! Publications, 1984): the MOS engineers volunteered for the small computer (p. 46); “a likable shirtsleeves manager” (p. 79); the C64 team of Winterble, Charpentier and Yannes (p. 237).
- Tim Danton, The Computers That Made Britain (Raspberry Pi Press, 2021), chapter on the Commodore VIC-20: the VIC begun in late 1976, offered to other manufacturers, and Charpentier hiring Yannes.
- Commodore 64 Programmer’s Reference Guide (Commodore, 1982): the VIC-II’s display modes, colours, sprites and raster interrupt.
- Compute! issue 56, January 1985, p. 34: the Ensoniq Mirage at $1,700.