this time, the company also began developing its own 3D modelling kernel for MEDUSA. Around 1980, CIS partnered with Prime Computer (also known as PR1ME and PRUNE), a U.S.-based computer hardware provider. Prime had an option on the MEDUSA source code should CIS ever fail. Split – Computervision / Prime Computers product: 1983 till 1987 In 1983 the U.S. CAD company Computervision (CV) purchased CIS. Computervision already had a legacy CAD product called CADDS4, but was interested in obtaining some of the state-of-the-art MEDUSA technology. At the time, MEDUSA was available on the then newly released 32bit so-called super mini computers, whose most prominent distributors were DEC (VAX) and Prime Computer. In 1984 there was a fork in MEDUSA: Prime took its option to keep developing MEDUSA. This in effect created two different versions of MEDUSA: CIS MEDUSA (owned by Computervision, which ran on Prime and VAX minicomputers and later on Sun workstations) and Prime MEDUSA (which ran on Prime minicomputers and was later made available on Sun workstations as well). The file format of the two versions drifted apart, as did the command syntax and therefore macro language, as the two versions were developed in slightly different directions. In Germany in the mid 1980s one MEDUSA workplace with a CV colour graphics terminal and a 19 inch colour screen including the software license cost around 145,000 German Marks (DM). The central computer would cost as much again. Because of the high costs involved, many companies deploying CAD systems reverted to shift work for design staff to make best use of the systems. The first shift might run from six in the morning until two in the afternoon; the second from two until ten o’clock in the evening. Product of Prime Computers: 1987 till 1992 The split in MEDUSA development was merged when Prime Computers bought Computervision, with the promise to CV customers that VAX users would not be forced to switch to Prime workstations. This exercise took significantly longer than suggested by initial marketing statements and the elapsed time consumed represented a period in which the software failed to move forward at all. Furthermore, many users did not trust the siren’s song that all would be well. The combined effect was that many users changed their CAD system. This was at a time when the PC-based AutoCAD software was becoming successful and offered all the basic 2D design functionality