The Atari ST is a line of home computers from Atari Corporation and the successor to the Atari 8-bit family. The initial ST model, the 520ST, saw limited release in the spring of 1985. The Atari ST is the first personal computer to come with a bitmapped color GUI using a version of Digital Research's GEM released in February 1985. The 1040ST, released in 1986, is the first personal computer to ship with a megabyte of RAM in the base configuration and also the first with a cost-per-kilobyte of less than US$1. "ST" officially stands for "Sixteen/Thirty-two", which refers to the Motorola 68000's 16-bit external bus and 32-bit internals.