Commodore VIC-20 | Code Like It's 198x

In April 1980 Commodore’s senior managers met at a hotel near Slough to plan the coming year, and most of them wanted a colour version of the PET business computer to sell for around $1,000. Then Jack Tramiel walked in and asked for something else. Michael Tomczyk, his new assistant, remembered the request as “a low and inexpensive colour computer”. Less than nine months later Commodore showed that computer at the Consumer Electronics Show in Las Vegas, priced at $299.95. “We had broken the $300 price barrier,” Tomczyk wrote.

The VIC-20 was built around a video chip that MOS Technology had been unable to sell to anyone else. It had 5K of memory and a screen only 22 characters wide. Tomczyk, describing the day the first orders came in, called it Tramiel’s “winky-dinky 5K 22-column color home computer”. Commodore sold it in discount stores, advertised it on television with William Shatner and cut its price again and again. In September 1983 Video Games Player reported it as “the first computer to sell a million units”, and by the time Commodore stopped making it in the spring of 1984 it had sold more than two million.

Fast facts

Launch: Japan, autumn 1980, as the VIC-1001; shown in the United States in January 1981 and on sale there during 1981; in British shops by late 1981.
Price: $299.95 in the US. In Britain, Computer & Video Games listed it at £185 in December 1981, and a mail-order advert that November charged £189.95.
CPU: MOS 6502. Nick Hampshire’s VIC Revealed gives the clock on British (PAL) machines as 1.1082 MHz.
Memory: 5K of RAM, of which BASIC reports 3583 BYTES FREE at switch-on. 20K of ROM: 8K of BASIC, 8K of KERNAL (the operating system) and a 4K character generator.
Video: the VIC chip, 6560 for NTSC televisions and 6561 for PAL. 23 rows of 22 characters, 176×184 pixels, 16 colours, but not all of them for everything (see below).
Sound: three tone generators and a white noise generator in the VIC chip, with one master volume.
Expansion: a cartridge port for games and memory; Commodore sold 3K, 8K and 16K memory cartridges.
Discontinued: production stopped in the spring of 1984. The Commodore 16 replaced it.

A chip in search of a computer

MOS Technology’s engineers, in Al Charpentier’s LSI group, had designed the Video Interface Chip for games machines and similar devices. Tomczyk wrote that MOS had shown it at the 1978 Consumer Electronics Show “with the intention of attracting a manufacturer who wanted to use it in a videogame”, and that nobody bought it. Its data sheet lists “low cost CRT terminals, biomedical monitors, control system displays and arcade or home video games” as the intended uses.

Bob Yannes, a young MOS chip designer, built a prototype computer around it. When Tramiel asked for his cheap colour computer, that prototype became the starting point. Tim Danton’s history of the machine lists the VIC-20’s “many fathers”: Charpentier’s team, Yannes, Robert Russell, who turned the prototype into a working computer, Tomczyk, who fought for the project inside Commodore, and the Japanese engineers under Yashi Terakura who finished the production design.

Commodore launched it in Japan first. Tomczyk’s reasoning was that several Japanese companies were preparing cheap colour computers for the American market, and a cheaper Commodore on sale in Tokyo would make them stop and rethink. The VIC-1001 went on show at the Seibu department store in Tokyo in the autumn of 1980, with a keyboard that carried a Japanese alphabet alongside English capitals. Commodore Japan’s Tony Tokai took orders for more than a thousand on the first day, Tomczyk recalled, “which was fantastic in 1980 when the entire world population of personal computers was only a few hundred thousand”.

Selling it like an appliance

BYTE reviewed the American machine in May 1981. Gregg Williams wrote that a picture of it “might cause you to think $600 would be a fair price”, praised the keyboard as “the equal of any personal-computer keyboard”, and concluded that it was unexcelled “as a low-cost, consumer-oriented computer. Even with some of its limitations (eg: screen size of 23 rows by 22 columns, maximum programmable memory of 32 K bytes), it makes an impressive showing against more expensive microcomputers like the Apple II, the Radio Shack TRS-80, and the Atari 800.” He put the low price down to the custom video chip, which replaced several other chips, and to Commodore “manufacturing most of the VIC at in-house factories in Japan”.

At first Commodore sold it through the computer dealers who sold its PETs, and it did not take off. The change came when the company took it to mass-market retailers. The discount chain K mart was the first, and Tomczyk lists Montgomery Ward, Toys “R” Us, Target and, later, Sears and J. C. Penney among those who followed. Dealers complained that they could buy VICs more cheaply at K mart than from Commodore.

Kit Spencer, who moved from Commodore’s European operation to run its American marketing in late 1981, persuaded Tramiel to pay for a television campaign. The advertisements starred William Shatner, Captain Kirk of Star Trek, who “stepped from out of a field of stars and proclaimed the VIC-20 as the Wonder Computer of the eighties”. Tomczyk was at the shoot. The hardest part, he wrote, was finding Shatner “an alien-looking sweater he could wear to look trekkie without infringing on the Captain Kirk character, to which we didn’t have the rights”. Leonard Nimoy had been considered, but he was already advertising for Magnavox.

Then the price fell. In August 1982 Texas Instruments offered a $100 rebate that took its 99/4A down to $200, and Commodore answered by cutting its dealer price for the VIC by $40. By November 1982, Tomczyk recorded, the VIC “was selling for as low as $179”.

In Britain the machine arrived at the end of 1981. Computer & Video Games’ buyer’s guide that December called it “the much publicised baby of the range of microcomputers from Commodore of Slough”, reported that “deliveries to dealers have just started”, and tipped it “to be a hot games computer because of its colour graphics and low cost”. It met cheaper competition there from Sinclair, and in 1983 the Spectrum’s price cuts left the VIC looking expensive at £139.50.

What the VIC chip could do

The 6560’s data sheet lists “on-chip color generation (16 colors)”, a screen grid of up to 192 by 200 dots, “three independent, programmable tone generators”, a “white noise generator”, two analogue-to-digital converters, which read the game paddles, and “no CPU wait states or screen hash during screen refresh”: drawing the picture never slows a program down.

Commodore used less than the chip’s full grid. The standard screen is 23 rows of 22 characters, which BYTE noted was fewer characters per line than any of its competitors. Each character is 8 pixels square, so a fully bit-mapped screen would be 176 by 184 pixels, and the Programmer’s Reference Guide works out that it would need 4048 bytes. On an unexpanded machine that is most of the memory there is. The screen itself lives in ordinary RAM: BYTE printed the addresses, 7680 to 8185 for the characters and 38,400 to 38,905 for their colours, and a BASIC program could POKE straight into either.

The Programmer’s Reference Guide calls the sound channels “speakers”: three for music, covering overlapping ranges of three octaves each with 128 settings, and a fourth for noise. Each is switched on by poking a value into its own register, from 36874 to 36877, and one more register, 36878, sets the volume for all of them. The sound came out of the television’s speaker.

The palette is asymmetric

The sixteen colours are not all available for everything. Nick Hampshire’s VIC Revealed divides them into two groups by what is being coloured. The first eight, black, white, red, cyan, magenta, green, blue and yellow, “can be used for the foreground or video colour RAM stored colour, and the border”. All sixteen, adding orange, light orange, pink, light cyan, light magenta, light green, light blue and light yellow, are available “for the background colour, and for the auxiliary colour”, the extra colour used in multicolour mode. BYTE found the same thing in 1981: “Choose from sixteen background colors and eight border colors.”

So a VIC-20 screen can have a pink background but cannot have pink text. The extra eight are not simply brighter versions of the first eight: orange and pink are colours the first group does not contain at all. The limit comes from the job each colour does, not from how many colours the chip can make. Colour memory holds four bits for each character position, and the Programmer’s Reference Guide explains that a value from 8 to 15 puts that position into multicolour mode. That leaves three bits, and eight colours, for ordinary text. The border gets three bits of its register too, while the background gets four.

Adding memory moves the screen

Commodore’s leaflet for its memory cartridges shows how much a RAM pack changed. With the 3K cartridge the machine reported 6655 bytes free, with the 8K cartridge 11775 and with the 16K 19967. Several 8K cartridges in an expansion unit took BASIC to 29K, and machine-code programs to 40K.

Adding 8K or more also rearranged the memory map. The leaflet sets it out: “Screen memory moves to locations 4096-4607 ($1000-11FF)”, “Color memory moves to locations 37888-38399 ($9400-95FF)”, and “The BASIC program area starts at 4608 ($1200)”. The reason is that the VIC chip can only read the machine’s own internal memory, not the cartridge, so the screen has to stay at the bottom of that memory while BASIC grows upwards into the cartridge. COMPUTE!’s Third Book of VIC explained the consequence for anyone designing their own characters: “the area where BASIC was in the unexpanded VIC (4096-4607) is now screen memory”, and “we cannot put our custom characters anywhere in the VIC’s expansion RAM”.

A program that pokes the screen directly therefore behaves differently on an expanded machine unless it checks where the screen has gone. This is why VIC-20 software was sold for a particular memory size. A Llamasoft advertisement in Computer & Video Games in March 1983 listed Jeff Minter’s Gridrunner and Abductor for the unexpanded VIC, alongside other games that needed an 8K expansion.

Software

The first software was a scramble. Tomczyk hired young self-taught programmers, the “VIC Commandos”, to turn old black-and-white PET games into colour VIC games, and Commodore bought in Japanese cartridge games. Several of those ran into trouble at the June 1981 show, when Atari’s lawyers objected to games called VIC Invaders and Midnight Drive. Commodore renamed the first VIC Avenger, and turned an unlicensed Rally-X into Radar Rat Race, with mice chasing cheese. Commodore also licensed Scott Adams’s text adventures and arcade games from Bally-Midway, although the adventures needed 16K cartridges that were slow to arrive. Neil Harris, one of the Commandos, rewrote the user manual in two weeks on a typewriter, because the PET that Tomczyk had asked for had not arrived.

Magazines filled the gap with type-in listings, and the editors of Compute! collected their VIC programs and articles in COMPUTE!’s First Book of VIC in 1982, the first of several volumes.

The first to a million

The claim that the VIC-20 was the first computer to sell a million comes from Commodore’s side and from the press of the time, and no independent sales count has been found to test it. Tomczyk hoped in late 1981 that Commodore could become “the first company to sell a million computers in one year”. He records that Tramiel “saw the VIC reach a million units” at around the end of 1982. Video Games Player printed the claim as news in September 1983. At the January 1984 Consumer Electronics Show, Commodore’s stand had pedestals holding the “Two Millionth VIC” and the “One Millionth Commodore 64”.

The end came quickly after that. Compute!’s Gazette reported in August 1984 that Commodore “had stopped manufacturing the VIC this spring”, and estimated that about 2.2 million had been sold worldwide, 1.2 million of them in the United States. Compute! said in January 1985 that “more than two million VICs have been sold worldwide”, and that the $100 Commodore 16 had replaced it as Commodore’s entry-level machine. Its bigger successor, the Commodore 64, had already been on sale for more than a year, built in the VIC-20’s case.

Sources

Michael S. Tomczyk, The Home Computer Wars: An Insider’s Account of Commodore and Jack Tramiel (Compute! Publications, 1984): MOS failing to find a buyer for the VIC chip (p. 41) and showing it at the 1978 CES (p. 114); the keyboard meeting of August 1980 and the Japanese launch at Seibu (pp. 164-173); “winky-dinky 5K 22-column color home computer” and the first day’s orders (p. 173); the January 1981 CES and the $299.95 price (pp. 189-190); June 1981 CES games and Atari’s lawyers (p. 206); Kit Spencer, the Shatner campaign and the Bally-Midway and Scott Adams licences (pp. 226-228); K mart and the mass merchants (pp. 234-235); “the first company to sell a million computers in one year” (p. 235); the VIC at $179 in November 1982 (p. 237); the VIC reaching a million units (p. 251); the August 1982 price cuts (p. 267); the two-millionth VIC at the January 1984 CES (p. 283).
Tim Danton, The Computers That Made Britain (Raspberry Pi Press, 2021), chapter on the Commodore VIC-20: the April 1980 meeting near Slough and Tramiel’s request, the “many fathers”, Robert Russell, the VIC-1001 name, the VIC Commandos and Neil Harris’s manual, Kit Spencer on the move to consumer channels; the VIC at £139.50 in 1983 (chapter on the ZX Spectrum).
Gregg Williams, “The Commodore VIC 20 Microcomputer: A Low-Cost, High-Performance Consumer Computer”, BYTE, May 1981, pp. 46-64: the price, the keyboard, the Japanese version, the display and colours (pp. 47-50), screen and colour memory addresses (pp. 50-52), the conclusions (pp. 63-64).
Commodore, VIC-20 Programmer’s Reference Guide (Commodore/Howard W. Sams, 1982): 5K of RAM (p. 27); high-resolution screen size (p. 90); multicolour mode set by colour values 8 to 15 (p. 92); the sound registers (p. 95 onwards); the memory map with the BASIC, KERNAL and character ROMs (pp. 116, 175-177); the 6560 data sheet (p. 212).
Nick Hampshire, VIC Revealed (Duckworth, 1982): the border colour in three bits of its register, and the two colour groups (p. 137); the 1.1082 MHz clock (p. 154). Nick Hampshire, VIC Graphics (Duckworth, 1983), p. 9: the colour table.
Commodore, Personal Computing on the VIC-20 (1981), p. 14: the start-up screen.
Commodore, Using the 3K, 8K and 16K Memory Expanders (VIC-1210, VIC-1110, VIC-1111 leaflet, 1982): bytes free with each cartridge, the moved screen, colour memory and BASIC, the 29K and 40K limits.
COMPUTE!’s Third Book of VIC (Compute! Books, 1984), p. 172: custom characters on the expanded VIC.
COMPUTE!’s First Book of VIC (Compute! Books, 1982): title page.
Computer & Video Games, issue 1, November 1981, p. 31: Computer Supermarket advertisement, the VIC 20 at £189.95. Issue 2, December 1981, p. 97: buyer’s guide, £185, “deliveries to dealers have just started”. Issue 17, March 1983, p. 73: Llamasoft advertisement.
Video Games Player, September 1983, p. 9: “The Commodore VIC-20 is the first computer to sell a million units”.
Compute!’s Gazette, issue 14, August 1984, p. 6: production stopped in the spring; about 2.2 million sold worldwide, 1.2 million in the US.
Compute!, issue 56, January 1985, p. 12: production stopped by June 1984; more than two million sold; the Commodore 16 as replacement.