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. Evolution The VIC-20 went through several variations in its three and a half years of production. First-year models (1980) had a PET-style keyboard with a blocky font while most VIC-20s made during 1981 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. Decline The VIC-20 was a bestseller, becoming the first computer to sell over a million. In total, 2.5 million computers were manufactured. In summer 1982, Commodore unveiled the a more advanced machine with of RAM and considerably improved sound and graphics. Initial sales of the C64 were slow, but took off in mid-1983. The VIC-20 was widely available for under $90 by that time. Commodore discontinued the VIC-20 in January 1985. Perhaps the last new commercially available VIC-20 peripheral was the VIC-Talker, a speech synthesizer. Ahoy! wrote in January 1986, "Believe it or not, a new VIC accessory...We were as surprised as you." 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