Commodore VIC-20
The
VIC-20 (
Germany:
VC-20;
Japan:
VIC-1001) is an
8-bit home computer. It was made by
Commodore Business Machines, with 5
KB RAM and a
MOS 6502 CPU. The machine's external design was later used by the
Commodore 64 and
C16. The VIC-20 was released in Japan in
1980, and in the U.S. and Europe in
1981, roughly three years after Commodore's first personal computer, the
PET.
Origin, marketing
The VIC-20 was intended to be more economical than the PET computer. The VIC-20's video chip, the
MOS Technology VIC was a general-purpose color video chip designed by
Al Charpentier in
1977 and intended for use in inexpensive display terminals and game consoles, but Commodore couldn't find a market for the chip. With
Apple II gaining momentum with the advent of
VisiCalc in
1979,
Jack Tramiel wanted a product out that would compete in the same segment, to be presented at the January
1980 CES. For this reason
Chuck Peddle and
Bill Seiler started to design a computer named
TOI (The Other Intellect).
The TOI computer failed to materialize, much due to the fact that it required an 80-column character display which in turn required the MOS Technology 6564 chip, which could not be used since it required very expensive static RAM memory to operate fast enough. In the meantime, freshman engineer
Robert Yannes at MOS Technology (then a part of Commodore) had designed a computer in his home dubbed the
MicroPET and finished a prototype with some help from Al Charpentier and Charles Winterble. When Jack Tramiel was confronted with this prototype he immediately said he wanted it to be finished and order it to be mass produced following a limited demonstration on the CES, since the TOI had not yet been finished.
The very hackish prototype produced by Yannes had very little of the features required for a real computer, so
Robert Russell at Commodore headquarters had to coordinate and finish large parts of the design under the codename
Vixen. The parts contributed by Russell included a port of the operating system (kernel and BASIC intepreter) taken from
John Feagans design for the
Commodore PET, a character set with the characteristic
PETSCII, an
Atari 2600-compatible
joystick interface and the cartridge port. The serial
IEEE 488-derivative interface was designed by
Glen Stark. Some features, like the memory add-in board, were designed by Bill Seiler. At the time, Commodore had an oversupply of 1Kbit×4
SRAM chips, so Tramiel demanded that these be used in the new computer. The end result is arguably closer to the
PET or
TOI computers than to Yannes prototype, albeit with a 22-column VIC chip instead of the custom chips designed for the more ambitious computers.
While the PET was sold through authorized dealers, the VIC-20 primarily sold at retail, especially discount and toy stores, where it could compete more directly with game consoles. Commodore took out advertisements featuring actor
William Shatner of
Star Trek fame as its spokesman, asking, "Why buy just a video game?".
Although the VIC-20 was criticized in print as being underpowered, the strategy worked: in 1982 it was the best-selling computer of the year, with 800,000 machines sold, and in January 1983 it passed the 1 million unit mark—a first in computer history. At its peak, 9,000 units per day were produced, and a total of 2.5 million units were sold before it was discontinued in January
1985, when Commodore repositioned the C64 as its entry-level computer due to the forthcoming release of the
C128 and
Amiga (the latter taking Commodore into the
16-bit world).
Applications
Because of its small memory and low-resolution display compared to some other computers of the time, the VIC-20 was primarily used for educational software and games. However, productivity
applications such as home finance programs, spreadsheets, and communication terminal programs were also made for the machine. Its high accessibility to the general public meant that quite a few software developers-to-be cut their teeth on the VIC-20, being introduced to
BASIC programming, and in some cases going further to learn
assembly or
machine language. Several
computer magazines sold on newsstands, such as
Compute! and CBM-produced publications, offered programming tips and
type-in programs for the VIC-20. Many VIC users learned to program by entering, studying, running, and modifying these type-ins.
The ease of programming the VIC and availability of an inexpensive modem combined to give the VIC a sizeable library of
public domain and
freeware software, although much smaller than that of the C64. This software was distributed on
online services such as
CompuServe,
BBSs, and via user groups.
As for commercial software offerings, an estimated 300 titles were available on
cartridge, and another 500+ titles were available on tape. By comparison, the
Atari 2600, the most popular of the
video game consoles at the time, had a library of about 900 titles. Cartridge games were ready to play as soon as VIC-20 was turned on, as opposed to games on tape which required loading. Titles on cartridge included
Gorf,
Cosmic Cruncher,
Sargon II Chess, and many others.
One of the most popular cassette games was
Blitz, written by Simon Taylor and published by Commodore, selling many tens of thousands of copies, and remaining in the top ten computer games listings for six months. The game involved flying over a city of skyscrapers, and flattening the buildings one by one by bombing them until the city was flat. The aircraft descended a line at a time, and if your bombing had not been accurate enough, you would hit the skyscraper and crash.
Basic features
|
The VIC-20 BASIC startup screen. |
The VIC-20 had proprietary connectors for program/expansion cartridges and a
tape drive (PET-standard
Datassette). It came with 5
KB RAM, but 1.5 KB were used by the system for various things, like the video display (which had a rather unusual 22×23 char/line screen layout), and other dynamic aspects of the
ROM-resident
BASIC interpreter and
KERNAL (a low-level operating system). Thus, 3.5 KB of BASIC program memory for code and variables was available to the user of an unexpanded machine.
The computer also had a serial bus (a serial version of the PET's
IEEE-488 bus) for
daisy chaining
disk drives and printers; a
TTL-level "user port" with
RS-232 and
Centronics signals (most frequently used as RS-232, for connecting a
modem[The Commodore VICModem and later models connected directly to the user port's edge connector. But in order to connect the VIC to industry-standard modems and other RS-232 devices, the user needed to purchase a separate TTL-to-RS232 voltage converter box (standard TTL voltages lie between 0 and 5 V, while RS-232 uses +/- 12 V).]); and a single
DE-9 game controller port, compatible with the digital
joysticks and
paddle (game controller)s used with
Atari 2600 videogame consoles and, later, the C64 (the use of a standard port ensured ample supply of Atari-manufactured and other third-party joysticks; Commodore itself offered an Atari joystick under the Commodore brand.
Importantly, like most video game consoles at the time the VIC had a
cartridge port to allow for plug-in cartridges with games and other software as well as for adding memory to the machine. Port expander boxes were available from Commodore and other vendors to allow more than one cartridge to be connected at a time.
Memory expansion
The VIC-20's RAM was expandable with plug-in cartridges using the same expansion port as programs. RAM cartridges were available in several sizes: 3K (with or without an included BASIC extension ROM), 8K, 16K, 32K and 64K, the latter two only from third-party vendors. The internal memory map was reorganised with the addition of each size cartridge, leading to the situation that some programs would only work if the right amount of memory was present (to cater for this, the 32K cartridges had switches, and the 64K cartridges had software setups, allowing the RAM to be enabled in user-selected sections).
The most visible part of memory that was reorganised with differing expansion memory configurations was the video memory (with text and/or graphics display data). This was because the free memory had to remain contiguous for the BASIC interpreter to be able to use it. An unexpanded VIC had 1K of system memory, followed by a 3K "hole", then 4K of contiguous user memory up to address 8191. The 3K cartridge would fill the "hole", so on unexpanded and +3K VICs the video area was placed at the top of user memory (8K - 512). If an 8K or 16K cartridge was added instead, this memory appeared at addresses above 8K; the video memory was then placed at the start of user memory at 4K, just above the "hole", to provide the maximum amount of contiguous user memory.
Some 64K expansion cartridges allowed the user to copy
ROM images to RAM. The more advanced versions even contained an 80-character video chip and a patched BASIC interpreter which gave access to 48K of the memory and to the 80-column video mode. As the latter type of cartridges, marketed primarily in Germany, weren't released until late 1984—two years after the appearance of the more capable C64—they went by mostly unnoticed.
* The name "VIC" came from the
Video Interface Chip, which, despite its designation, also handled all the sound synthesis in the VIC-20. The VIC chip's successor, the graphics-and-RAM-refresh
VIC-II, was used to great success in Commodore's later best-selling machine, the C64, and also in the dual video output C128 for that computer's 40-column/composite video graphics.
* The VIC-20 was originally meant to be called
Vixen, but this name was inappropriate in
Germany, Commodore's second most important market, because it sounds like
wichsen, the
German language word for "masturbate". VIC, which was subsequently chosen, has a similar problem—it can be pronounced like
fick[en], the German word for "fuck". Therefore the VIC-20 was finally marketed as the
VC-20 "Volkscomputer" in German-language countries—an obvious play on "
Volkswagen".
* In
Japan the VIC-20 was marketed as the
VIC-1001 (
1980).
*
BASIC programs running on a fully expanded VIC-20 could use at most 24K RAM. Any extra occupied the memory space used by ROM cartridges, i.e. commercial software like games and other applications. This allowed people to copy cartridges to tape and distribute them to their friends, who could then load the tape into the top 8K of their 32K RAM packs.
* An anecdotal bit of evidence to support Commodore's statement that the VIC-20 could be used not only for games but also as a serious introduction to computing, can be said to originate in the fact that a young
Linus Torvalds was given a VIC-20 as his first computer. Torvalds later upgraded to a
Sinclair QL, then to a
386 PC. Torvalds later went on to write the
Linux operating system kernel.
Both the VIC 20 and C64 could be hooked into external electronic circuitry, using parts available from Radio Shack stores or other parts outlets. Interfaces were designed to use either the joystick ports, printer port, or the expansion ports, which exposed various analog to digital, memory bus, and other internal I/O circuits to the experimenter. The BASIC language could then be used (using the PEEK and POKE commands) to perform data acquisition from tempterature senors, control robotic stepper motors, etc. The VIC 20 did not originally have a disk drive available for sale, with only a relatively high cost tape recorder system (using audio cassette tapes). Many experimenters built adaptors that allowed any conventional audio cassette recorder to be used for program and data storage.
* Bagnall, Brian:
On The Edge: The Spectacular Rise and Fall of Commodore, ISBN 0-9738649-0-7.
* Finkel, A.; Harris, N.; Higginbottom, P.; Tomczyk, M. (1982).
VIC 20 Programmer's reference guide. Commodore Business Machines, Inc. and Howard W. Sams & Co, Inc. ISBN 0-672-21948-4.
* Jones, A. J.; Coley, E. A.; Cole, D. G. J. (1983).
Mastering the VIC-20. Chichester, UK: Ellis Horwood Ltd. and John Wiley & Sons, Inc. ISBN 0-471-88892-3.
* Tomczyk, Michael (1984).
The Home Computer Wars: An Insider's Account of Commodore and Jack Tramiel. COMPUTE! Publications, Inc. ISBN 0-942386-75-2.
*
Denial - the Commodore VIC-20 Community*
OLD-COMPUTERS.COM online-museum VIC-20 page*
Commodore VIC-20 Tribute Page, by Rick Melick*
Archive.org commercial for the VIC-20 featuring William Shatner Full length version of same commercial*
Collection of old analog and digital computers at www.oldcomputermuseum.com*
1000BiT.net - Commodore VIC-20 page*
1000BiT.net - Commodore VIC-1001 page*
1000BiT.net - Commodore VC-20 page
