Graphics in time-sharing: a summary of the TX-2 experience

The TX-2 computer, an experimental machine at the M.I.T. Lincoln Laboratory, has been in operation for almost 10 years as an on-line, graphically oriented facility. In 1964, a time-sharing system for the TX-2 was started. This system, APEX, was to service a small number of consoles with graphic display capability. To achieve hardware economy, displays were to be refreshed from main core memory through a time-shared vector generator providing analog signals distributed to the individual console scopes. The displays were to be refreshed directly from a structured display file as experience with the Sketchpad developments of the early 1960's had indicated was highly desirable for interactive graphic applications. Although the APEX graphic system has evolved through several generations of display hardware and corresponding software changes, the initial design principles of displays refreshed from structured information in main core by a time-shared generator have remained. This paper is an attempt to collect and evaluate some lessons learned from our experience in developing and using this system.