After successful test marketing in 1979, Mattel Electronics released its Intellivision system nationwide in late 1980. Armed with twelve games, better graphics and sound than its competitors, and the promise to release a compatible keyboard that would turn the system into a home computer ("Play games and balance your checkbook!"), Mattel set its sights on taking down the "invincible" Atari 2600. They got off to a good start, selling out the first production run of 200,000 Intellivision units quickly.
Mattel also released the system under different names to expand its market. The Intellivision was released in Sears stores as the Super Video Arcade, at Radio Shack as the Tandyvision I, and as the GTE/Sylvania Intellivision.
Many people bought an Intellivision with plans to turn it into a home computer when the keyboard was released. There was a huge marketing campaign behind this (one-third of the back of the Intellivision box was dedicated to the "Under Development" keyboard), but months and then years passed without the keyboard being released. Actually, it was released in a few test markets in late '81, but the price was too high and the initial reaction poor. So in 1982, Mattel scrapped plans for the infamous keyboard, but later (due to government pressure), they had to make a computer add-on anyway (see below). Read more at classicgaming.com