YAMHILL, Ore.--There is a story behind every electronic gadget sold on the QVC shopping channel. This one leads to a ramshackle farmhouse in rural Oregon, which is the home and circuit design lab of Jeri Ellsworth, a 30-year-old high school dropout and self-taught computer chip designer. Ellsworth has squeezed the entire circuitry of a two-decade-old Commodore 64 home computer onto a single chip, which she has tucked neatly into a joystick that connects by a cable to a TV set. Called the Commodore 64--the same as the computer system--her device can run 30 video games, mostly sports, racing and puzzles...