Commodore VIC-20
The VIC-20 is an 8-bit home computer that was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET. The VIC-20 was the first computer of any description to sell one million units. It was described as "one of the first anti-spectatorial, non-esoteric computers by design...no longer relegated to hobbyist/enthusiasts or those with money, the computer Commodore developed was the computer of the future."
The VIC-20 was called VC-20 in Germany because the pronunciation of VIC with a German accent sounds like the German expletives "fick" or "wichsen". The term VC was marketed as though it was an abbreviation of VolksComputer.
History
Origin and marketing
The VIC-20 was intended to be more economical than the PET computer. It was equipped with 5 KB of static RAM and used the same MOS 6502 CPU as the PET. 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 could not find a market for the chip.As the Apple II gained momentum with the advent of VisiCalc in 1979, Jack Tramiel wanted a product 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 TOI computer failed to materialize, mostly because it required an 80-column character display which in turn required the MOS Technology 6564 chip. However, the chip could not be used in the TOI since it required very expensive static RAM to operate fast enough.
In the meantime, freshman engineer Robert Yannes at MOS Technology had designed a computer in his home dubbed the MicroPET and finished a prototype with some help from Al Charpentier and Charles Winterble. With the TOI unfinished, when Jack Tramiel was shown the MicroPET prototype, he immediately said he wanted it to be finished and ordered it to be mass-produced following a limited demonstration at the CES.
As the new decade began, the price of computer hardware was dropping and Tramiel saw an emerging market for low-price computers that could be sold at retail stores to relative novices rather than professionals or people with an electronics or programming background. The personal computer market up to this point had sold primarily through mail order or authorized dealers, the sole exception being Radio Shack, who had their own stores as a distribution network. Radio Shack had been achieving considerable success with the TRS-80 Model I, a relatively low-cost machine that was widely sold to novices and in 1980 released the Color Computer, which was aimed at the home and educational markets, utilized ROM cartridges for software, and connected to an ordinary TV set.
The prototype produced by Yannes had very few 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 taken from John Feagans design for the Commodore PET, a character set with the characteristic PETSCII, an Atari 2600-compatible joystick interface, and a ROM cartridge port. The serial IEEE-488-derivative CBM-488 interface was designed by Glen Stark. It served several purposes, including costing substantially less than the IEEE-488 interface on the PET, using smaller cables and connectors that allowed for a more compact case design, and also complying with newly-imposed FCC regulations on RFI emissions by home electronics. Some features, like the memory add-in board, were designed by Bill Seiler. Altogether, the VIC 20 development team consisted of five people led by Michael Tomczyk the product manager, who recruited the group and dubbed them the VIC Commandos. Commodore founder Jack Tramiel initially gave Tomczyk the title VIC Czar and later appointed him product manager. Tomczyk insisted on several features including full size typewriter keys, programmable function keys and a built-in RS-232 interface. Michael later contracted and co-designed a $100 modem, the VICModem, which became the first modem to sell 1 million units. According to one of the development team, Neil Harris, "e couldn't get any cooperation from the rest of the company who thought we were jokers because we were working late, about an hour after everyone else had left the building. We'd swipe whatever equipment we needed to get our jobs done. There was no other way to get the work done! they'd discover it was missing and they would just order more stuff from the warehouse, so everybody had what they needed to do their work." At the time, Commodore had a glut of SRAM chips, so Tramiel decided these should be used in the new computer. The end result was 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. As the amount of memory on the VIC-20's system board was very small even for 1981 standards, the design team could get away with using more expensive SRAM due to its lower power consumption, heat output, and less supporting circuitry. The original Revision A system board found in all silver-label VIC-20s used 2114 SRAMs and due to their tiny size, ten of them were required to reach 5 KB of system RAM. The Revision B system board, found in rainbow logo VIC-20s switched to larger 2048-byte SRAMs which reduced the memory count to five chips: 2× 2048-byte chips + 3× 2114 chips.
While newer PETs had the upgraded BASIC 4.0, which had disk commands and improved garbage collection, the VIC-20 reverted to the 8 KB BASIC 2.0 used on earlier PETs as part of another of the design team's goals, which was limiting the system ROMs to only 20 KB. Since Commodore's BASIC had been designed for the PET which had only limited audiovisual capabilities, there were no dedicated sound or graphics features, thus VIC-20 programmers had to use large numbers of POKE and PEEK statements for this. This was in contrast to the computer's main competitors, the Atari 400 and TRS-80 Color Computer, both of which had full-featured BASICs with support for the machines' sound and graphics hardware. Supplying a more limited BASIC in the VIC-20 would keep the price low and the user could purchase a BASIC extender separately if he desired sound or graphics commands.
While the TRS-80 Color Computer and Atari 400 had only RF video output, the VIC-20 instead had composite output, which provided a sharper, cleaner picture if a dedicated monitor was used. An external RF modulator was necessary to use the computer with a TV set, and had not been included internally so as to comply with FCC regulations.
VIC-20s went through several variations in their three and a half years of production. First-year models had a PET-style keyboard with a blocky font while most VIC-20s made during 1982 had a slightly different keyboard also shared with early C64s. The rainbow logo VIC-20 was introduced in early 1983 and has the newer C64 keyboard with gray function keys and the Revision B motherboard. It has a similar power supply to the C64 PSU, although the amperage is slightly lower. A C64 "black brick" PSU is compatible with Revision B VIC-20s; however, the VIC's PSU is not recommended on a C64 if any external devices such as cartridges or user port accessories are installed as it will overdraw the available power. Older Revision A VIC-20s cannot use a C64 PSU or vice versa as their power requirement is too high.
In April 1980, at a meeting of general managers outside London, Jack Tramiel declared he wanted a low-cost color computer. When most of the GMs argued against it, he said: "The Japanese are coming, so we will become the Japanese." This was in keeping with Tramiel's philosophy which was to make "computers for the masses, not the classes". The concept was championed at the meeting by Michael Tomczyk, newly hired marketing strategist and assistant to the president, Tony Tokai, General Manager of Commodore-Japan, and Kit Spencer, the UK's top marketing executive. Then, the project was given to Commodore Japan; an engineering team led by Yash Terakura created the VIC-1001 for the Japanese market. The VIC-20 was marketed in Japan as VIC-1001 before VIC-20 was introduced to the US.
When they returned to California from that meeting, Tomczyk wrote a 30-page memo detailing recommendations for the new computer, and presented it to Tramiel. Recommendations included programmable function keys, full-size typewriter-style keys, and built-in RS-232. Tomczyk insisted on "user-friendliness" as the prime directive for the new computer, to engineer Yash Terakura, and proposed a retail price of. He recruited a marketing team and a small group of computer enthusiasts, and worked closely with colleagues in the UK and Japan to create colorful packaging, user manuals, and the first wave of software programs.
Scott Adams was contracted to provide a series of text adventure games. With help from a Commodore engineer who came to Longwood, Florida to assist in the effort, five of Adams's Adventure International game series were ported to the VIC. They got around the limited memory of VIC-20 by having the games reside in a ROM cartridge instead of being loaded into main memory via cassette as they were on the TRS-80 and other machines. The first production run of the five cartridges generated over $1,500,000 in sales for Commodore.
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. It was the first computer to be sold in K-Mart. Commodore took out advertisements featuring actor William Shatner as its spokesman, asking: "Why buy just a video game?" and describing it as "The Wonder Computer of the 1980s". Television personality Henry Morgan became the commentator in a series of Commodore product ads.
The VIC-20 had 5 KB of RAM, of which only 3.5 KB remained available on startup. This is roughly equivalent to the words and spaces on one sheet of typing paper, meeting a design goal of the machine. The computer was expandable up to 40 KB with an add-on memory cartridge.
The "20" in the computer's name was widely assumed to refer to the text width of the screen or that it referred to the combined size of the system ROMs. Bob Yannes claimed that "20" meant nothing in particular and "We simply picked '20' because it seemed like a friendly number and the computer's marketing slogan was 'The Friendly Computer'. I felt it balanced things out a bit since 'Vic' sounded like the name of a truck driver."
In 1981, Tomczyk contracted with an outside engineering group to develop a direct-connect modem-on-a-cartridge, which at US$99 became the first modem priced under US$100. The VICModem was also the first modem to sell over 1 million units. VICModem was packaged with US$197.50 worth of free telecomputing services from The Source, CompuServe and Dow Jones. Tomczyk also created a SIG called the Commodore Information Network to enable users to exchange information and take some of the pressure off of Customer Support inquiries, which were straining Commodore's lean organization. In 1982, this network accounted for the largest traffic on CompuServe.
Applications
The VIC-20's BASIC is compatible with the PET's, and the Datasette format is the same. Before the computer's release, a Commodore executive promised it would have "enough additional documentation to enable an experienced programmer/hobbyist to get inside and let his imagination work". Compute! favorably contrasted the company's encouragement of "cottage industry software developers" to Texas Instruments discouraging third-party software. 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.The VIC had a sizable library of public domain and freeware software. This software was distributed via online services such as CompuServe, BBSs, as well as offline by mail order and by user groups. Several computer magazines sold on newsstands, such as Compute!, Family Computing, RUN, Ahoy!, and the CBM-produced Commodore Power Play, offered programming tips and type-in programs for the VIC-20.
An estimated 300 commercial titles were available on cartridge and another 500+ were available on tape. A handful of disk applications were released.
The VIC's low cost led to it being used by the Fort Pierce, Florida Utilities Authority to measure the input and output of two of their generators and display the results on monitors throughout the plant. The utility was able to purchase multiple VIC and C64 systems for the cost of one IBM PC compatible.
Decline
The VIC-20 was the best-selling computer of 1982, with 800,000 machines sold. One million units had been sold by the end of the first full year of production; at one point, 9,000 units a day were being produced. That summer, Commodore unveiled the a more advanced machine with of RAM and considerably improved sound and graphics capabilities. Sales of the C64 were slow at first due to reliability problems and lack of software. But by the middle of 1983, sales of the C64 took off resulting in plunging sales for the VIC-20. In order to try and staunch the sales decline, by mid-1983 the computer had become widely available for under $90. As sales of the computer continued to decline, the VIC-20 was quietly discontinued in January 1985. Perhaps the last new commercially available VIC-20 peripheral was the VIC-Talker, a speech synthesizer; Ahoy! in January 1986 wrote when discussing it, "Believe it or not, a new VIC accessory...We were as surprised as you."Technical specifications
The VIC-20 shipped with RAM, but of this was used by the system for the video display and dynamic aspects of the ROM-resident Commodore BASIC and KERNAL. Only 3583 bytes of BASIC program memory for code and variables are actually available on an unexpanded machine.Ports and sockets
The VIC-20 has card edge connectors for program/expansion cartridges and a PET-standard Datassette tape drive. The VIC-20 did not originally have a disk drive; the VIC-1540 disk drive was released in 1981.The computer also has a single DE-9 Atari joystick port, compatible with the digital joysticks and paddles used with Atari 2600 videogame consoles ; a serial CBM-488 bus for daisy chaining disk drives and printers; a TTL-level "user port" with both RS-232 and Centronics signals.
The VIC has a ROM 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 attached at a time. Cartridge software ranged from in size, although the latter was uncommon due to its cost.
The VIC-20 can be hooked into external electronic circuitry via joystick port, the so-called "user port," or the memory expansion–cartridge port, which exposes various analog to digital, memory bus, and other internal I/O circuits to the experimenter. The BASIC language can then be used to perform data acquisition from temperature sensors, control robotic stepper motors, etc.
Graphics
The graphics capabilities of the VIC chip are limited but flexible. At startup the screen shows 176×184 pixels, with a fixed-color border to the edges of the screen. Since a PAL or NTSC screen has a 4:3 width-to-height ratio, each VIC pixel is much wider than it is high. The screen normally shows 22 columns and 23 rows of 8-by-8-pixel characters; it is possible to increase these dimensions up to 27 columns, but the characters would soon run out the sides of the monitor at about 25 columns. Just as on the PET, two different 256 character sets are included, the uppercase/graphics character set and the upper/lowercase set, and reverse video versions of both. Normally, the VIC-20 operates in high-resolution mode whereby each character is 8×8 pixels in size and uses one color. A lower-resolution multicolor mode can also be used with 4×8 characters and three colors each, but it is not used as often due to its extreme blockiness.The VIC chip does not support a true bitmap mode, but programmers can define their own custom character sets. It is possible to get a fully addressable screen, although slightly smaller than normal, by filling the screen with a sequence of different double-height characters, then turning on the pixels selectively inside the RAM-based character definitions. The Super Expander cartridge adds BASIC commands supporting such a graphics mode using a resolution of 160×160 pixels. It is also possible to fill a larger area of the screen with addressable graphics using a more dynamic allocation scheme, if the contents are sparse or repetitive enough. This is used by the port of Omega Race.
The VIC chip has readable scan-line counters but cannot generate interrupts based on the scan position. The two VIA timer chips can serve this purpose through an elaborate programming technique, allowing graphics to mixed with text above or below it, two different background and border colors, or more than 200 characters for the pseudo-high-resolution mode.
The VIC chip can process a light pen signal but few appeared on the market.
The VIC chip outputs composite video. Commodore did not include an RF modulator inside the computer's case because of FCC regulations. It can either be attached to a dedicated monitor or a TV set using the external modulator included with the computer.
Sound
The VIC chip has three pulse wave generators and a white noise generator with an overall volume control and mono output. Each pulse wave generator has a range of three octaves located on the scale about an octave apart, giving a total range of about five octaves.Memory expansion
Because the VIC had only 5K RAM, the VIC-20's RAM was expandable through the cartridge port via a Super Expander Cartridge. RAM cartridges were available in several sizes: ,,, and, the latter two only from third-party vendors. The internal memory map was dramatically reorganized with the addition of each size cartridge, leading to a situation where some programs would only work if the right amount of memory was present. Since the VIC-20 was designed to use SRAM rather than DRAM, the system board had no provisions for DRAM refresh.The memory mapping of the VIC-20 was slightly confusing and could vary depending on system configuration. With no expanders installed, free user memory started at $1000 and extended up to $1DFF, with the video buffer placed at $1E00-$1FFF. Below $1000 was a "hole" from $400-$FFF which could be filled with of expansion RAM, which if installed would place the BASIC program area at $400. If an or larger expander was used, screen memory began at $1000 and BASIC program text at $1200.
The VIC-20 allowed two locations for color RAM, either at $9600 or $9400. The default for unexpanded machines was at $9600, and with an or larger expander, the color RAM would be moved to $9400, however the user could freely set it to either location via the register at $9002.
The normal location for ROM cartridges was at $A000–$BFFF. On power up, the kernel ROM checked for an ID header and if found would jump to the specified starting address. Larger cartridges had the second half of ROM either at $2000 or $6000. A few cartridges, including Scott Adams adventures, loaded entirely in the $2000-$7FFF area. Since the kernel can only autostart ROMs located at $A000, such programs would have to be manually launched from BASIC via the SYS command.
Commodore's official RAM expansion cartridges were only available up to a maximum of worth of additional memory, but third party cartridges could provide up to and sometimes included DIP switches to map the additional RAM to user-selectable address space.
Unlike the PET, the VIC-20 did not include a built-in machine language monitor, but Commodore offered them on disk, tape, or cartridge, with several different executables to load into various memory locations. The monitor programs were the same as the PET monitor, but now added a mini-assembler instead of requiring the user to enter hexadecimal opcodes.
The cartridges allowed adding up to to the BASIC user memory; together with the built-in user memory, this gave a maximum of for BASIC programs and variables. The extra could usually be used in one of two ways, set by switches:
- Either it could be mapped into the address space reserved for ROM cartridges, which sat "behind" the I/O register space and thus was not contiguous with the rest of the RAM. This allowed running many cartridge-based games from disk or tape and was thus very useful for software pirates; especially if the RAM expansion allowed switching off writing to its memory after the game was loaded, so that the memory behaved exactly like ROM.
- Or, of the could be mapped into the same memory "hole" that the cartridge used, letting lie fallow. These were contiguous with the rest of RAM, but couldn't be used to expand BASIC space to more than, because the display data would have had to be moved to cartridge RAM, which was not possible.
| Address | Size [in KB] | Description | Cartridge decoded |
| 0x0000 | 1.0 | RAM with jump vectors etc. | |
| 0x0400 | 3.0 | Expansion | * |
| 0x1000 | 4.0 | RAM for BASIC and screen | |
| 0x2000 | 8.0 | Expansion block 1 | * |
| 0x4000 | 8.0 | Expansion block 2 | * |
| 0x6000 | 8.0 | Expansion block 3 | * |
| 0x8000 | 4.0 | ROM character bitmap | |
| 0x9000 | 1.0 | I/O for VIC, 6522 VIA#1, 6522 VIA#2, block 0 | |
| 0x9400 | 0.5 | Used for color RAM when expansion RAM at block 1 | |
| 0x9600 | 0.5 | Color RAM | |
| 0x9800 | 1.0 | I/O block 2 | * |
| 0x9C00 | 1.0 | I/O block 3 | * |
| 0xA000 | 8.0 | Decoded for expansion ROM | * |
| 0xC000 | 8.0 | ROM BASIC | |
| 0xE000 | 8.0 | ROM KERNAL |