The system architecture was based on the Intel 80186, with proprietary VLSI chips that enhanced and sped up the graphics. Although it was disk compatible with the IBM PC's DOS, its enhanced graphics capabilities made achieving full IBM compatibility more difficult than its competitors. Bill Gates became involved with development, assisting Mindset in emulating IBM character graphics without losing performance. Once Mindset officials determined that most of the desirable software was compatible, development was frozen and the OS burned to ROM, which locked out 20% of the PC software base, including "Microsoft Flight Simulator". WordStar was one of the PC applications reported to run, and Mindset publicized a list of 60 applications that ran unmodified. The software base was expected to increase dramatically once a final version of Windows was released.