To reduce production costs, Mattel Electronics introduced the sleeker and much smaller Intellivision II Master Component, a white and black unit with removable controllers and an external power supply.
Another "feature" was a secret validation check in the hardware that made third-party software inoperable. This check affected Coleco's 1982 arcade conversions -- Donkey Kong, Mouse Trap, and Carnival -- and inadvertently rendered Mattel's own Electric Company Word Fun (1980) unplayable. Fortunately, internal and external development groups soon figured out how to bypass the check.
Finally, a special video input added to the cartridge port made the System Changer possible, which allowed the Intellivision II to play Atari VCS games. All other Intellivision systems required internal modification to use the System Changer.
In 1983, the second computer add-on, the Enhanced Computer System (ECS), was released, retailing for less than $150. The ECS, like the System Changer, matched the styling of the Intellivision II, though it was compatible with all Intellivision models and the Intellivoice.
The ECS featured a detachable chiclet keyboard, an expansion box, and power supply. It also added an extra 2KB of memory, three extra channels of sound, two additional controller ports, and the ability to accept a standard tape recorder and a printer, the latter being the same as the one for the original Keyboard Component and Mattel Aquarius computer. A simplified version of BASIC was built in along with the ability to play musical tones.
An Intellivision II with ECS module, keyboard and music keyboard, along with an Intellivoice module.