The VIC-20 (in Germany: VC-20; In Japan: VIC-1001) 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.
* 1 History
* 1.1 Origin, marketing * 1.2 Decline * 1.3 Applications
* 2 Technical specifications
* 2.1 Basic features
* 2.1.1 Ports and sockets * 2.1.2 Graphics * 2.1.3 Sound
* 2.2 Memory expansion
* 3 Reception * 4 Notes * 5 See also * 6 References * 7 Further reading * 8 External links
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.
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. With the TOI unfinished, when Jack Tramiel was confronted with 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.
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 (kernel and BASIC interpreter) taken from
John Feagans design for the
Commodore PET , a character set with the
PETSCII , an
VIC-20s went through several variations in their 3-1/2 years of production. First-year models (1981) 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. The VIC-1001 was the Japanese version of the VIC-20. It featured Japanese-language characters in the ROM and on the front of the keys.
In April 1980, at a meeting of general managers outside London, Jack Tramiel declared that 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. The Commodore 1530 C2N-B Datasette provided inexpensive external storage for the VIC-20
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 (inspired by competing Japanese computers), 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 (who was also a friend), and proposed a retail price of US$299.95. 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 (mostly games and home applications).
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 16 KB games reside in a ROM
cartridge instead of being loaded into main memory via cassette as
they were on the
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
William Shatner (of
The VIC-20 had 5 KB of RAM, of which only 3.5 KB remained available on startup (exactly 3583 bytes). 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 (a maximum of 27.5 KB was usable for BASIC). Although the VIC-20 was criticized in print as being underpowered, the strategy worked.
The "20" in the computer's name was the source of some debate as to its meaning. It was widely assumed that it referred to the text width of the screen (although in fact the VIC-20 had 22-column text, not 20) or that it referred to the combined size of the system ROMs (8k BASIC+8k kernel+4k character ROM). 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 (the VIC
In 1982, the VIC-20 was the best-selling computer of the year, with
800,000 machines sold. One million had been sold by the end of the
year and at one point, 9000 units a day were being produced. That
summer, Commodore unveiled the
The VIC-20's BASIC is compatible with the PET's, except for PEEK and
POKE commands, and the
Datasette format is the same. Before the
computer's release, a Commodore executive promised that it would have
"enough additional documentation to enable an experienced
programmer/hobbyist to get inside and let his imagination work".
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
An estimated 300 commercial titles were available on cartridge and another 500+ were available on tape. Most cartridge games were ready to play as soon as the VIC-20 was turned on, as opposed to games on tape which required a time-consuming loading process. Titles on cartridge included Gorf , Radar Rat Race , Sargon II Chess , and Jupiter Lander. 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 C-64 systems for the cost of one IBM PC Compatible system.
Ports And Sockets
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 of this was 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, only 3583 bytes of BASIC program memory for code and variables was actually available to the user of an unexpanded machine.
The computer also had a single DE-9
Atari joystick port , compatible
with the digital joysticks and paddles used with
Importantly, like most video game consoles and many computers at the time the VIC had 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 4 - 16 KB in size, although the latter was uncommon due to its cost and only larger software houses produced 16 KB cartridges.
16-color (multicolor) capability
The graphics capabilities of the VIC chip (6560/6561) were limited but flexible. At startup the screen showed 176×184 pixels, with a fixed-colour border to the edges of the screen; since an NTSC or PAL screen has a 4:3 width-to-height ratio, each VIC pixel was much wider than it was high. The screen normally showed 22 columns and 23 rows of 8-by-8-pixel characters; it was 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, 256 different characters could be displayed at any one time, normally taken from one of the two character generators in ROM (one for upper-case letters and simple graphics, the other for mixed-case; non-English characters were not provided). Normally, the VIC-20 was operated in high-resolution mode whereby each character was 8×8 pixels in size and used one color. A lower-resolution multicolor mode could also be used with 4×8 characters and three colors each, but it was not used as often due to its extreme blockiness.
The VIC chip did not support a true bitmap mode, but programmers could define their own custom character set. It was 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 added BASIC commands supporting such a graphics mode using a resolution of 160×160 pixels. It was also possible to fill a larger area of the screen with addressable graphics using a more dynamic allocation scheme, if the contents were sparse or repetitive enough. This was used, for instance, by the game Omega Race . The VIC chip did not support sprites .
The VIC chip had readable scan-line counters but could not generate interrupts based on the scan position (as the VIC-II chip could). However, the two VIA timer chips could be tricked into generating interrupts at specific screen locations, by setting up the timers after a position had been established by repetitive reading of the scan-line counter, and letting them run the exact number of cycles that pass by during one full screen update. Thus it was possible, but difficult, to e.g. mix graphics with text above or below it, or to have two different background and border colors, or to use more than 200 characters for the pseudo-high-resolution mode. The VIC chip could also process a light pen signal (a light pen input was provided on the DE-9 joystick connector) but few of those ever appeared on the market.
The VIC chip output composite video; Commodore did not include an RF modulator inside the computer's case because of FCC regulations. It could either be attached to a dedicated monitor or a TV set using the external modulator included with the computer.
The VIC chip had three pulse wave sound generators. Each had a range of three octaves , and the generators were located on the scale about an octave apart, giving a total range of about five octaves. In addition, there was a white noise generator. There was only one volume control, and the output was in mono.
A 16 kB RAM expansion cartridge
Because the VIC had only 5K RAM, the VIC-20's RAM was expandable through the cartridge port via. Super Expander Cartridge (or simply, RAM Expander). RAM cartridges were available in several sizes: 3 kB (with or without an included BASIC extension ROM), 8 kB, 16 kB, 32 kB and 64 kB, 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 (to cater to this, the 32 kB cartridges had switches, and the 64 kB cartridges had software setups, allowing the RAM to be enabled in user-selectable memory blocks).
Since the VIC-20 was designed to use SRAM rather than DRAM, the system board had no provisions for RAM refresh. Memory expansion cartridges may in practice use either type; however, DRAM-based expanders had to contain their own circuitry to refresh the RAM and multiplex the data/address bus, and one possible reason for the oversized VIC-20 cartridge PCBs may have been to provide room for DRAM infrastructure.
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 3 kB of expansion RAM. If memory expansion cartridges were used, video memory started at $1000 and free user RAM at $1200.
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 16 kB 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 16 kB worth of additional memory, but third party cartridges could provide up to 64 kB 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 32 kB cartridges allowed adding up to 24 kB to the BASIC user memory; together with the 3.5 kB built-in user memory, this gave a maximum of 27.5 kB for BASIC programs and variables. The extra 8 kB 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, 3 kB of the 8 kB could be mapped into the same memory "hole" that the 3 kB cartridge used, letting 5 kB lie fallow. These 3 kB were contiguous with the rest of RAM, but couldn't be used to expand BASIC space to more than 27.5 kB, because the display data would have had to be moved to cartridge RAM, which was not possible.
Some 64 kB 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 48 kB of the memory and to the 80-column video mode. As the latter type of cartridges, marketed primarily in Germany, were not released until late 1984—two years after the appearance of the more capable C64 —they went by mostly unnoticed.
Memory map ADDRESS SIZE 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 (normally)
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
Describing it as "an astounding machine for the price",
The VIC-20 could be hooked into external electronic circuitry, using
parts available from parts outlets like
As on other Commodore 8-bit systems, certain system functions could be accessed by the SYS command . For example, even though the VIC had no hardware reset button, SYS 64802 would cause the computer to reset, because memory location 64802 in the standard memory map was the entry point to the VIC's KERNAL reset routine.
* ^ "MESS VIC20/VC20 (German) PAL". MESS — Multiple Emulator
* ^ "Home Video Game Console Sound Chip Round-Up". 090514
* ^ The computer was renamed in German-speaking countries because
"VIC" would be pronounced similarly to the obscene word fick.