Multiprogramming in a small-systems environment
David L. Mills · 1969
1___Introductio nThis paper describes developments o f the RAMP system, a m ultiprogramming syste m designed for use in small machines of th e PDP°8 class for operation in real-tim e processing environments .Several of thes e systems ace currently operating in proces s control, message switching and termina l control applications .The development o f this system was largely the result of th e need for relatively sophisticated dat a communications systems for use by remotel y located process control and interactiv e graphics terminals .Early versions o f this system, as described in [1, 2, an d 3], sustained aggregate transmission rate s of about 500-1000 characters-per-secon d for as many as twenty-four terminals .Further uevelopment has resulted i n an enhanced throughput and an attractiv e interface to which special-purpose jobprogram subsystems can be attached [4] .The newer system incorporate a genera l storage allocation technique whic h provides both for the dynamic loading o f page-relocatable job-program subsystem s and for the temporary storage of contro l information and I/O buffers .The concep t of task, program, and real/task-tim e processing is given precise definition , and the interface to device servic e routines is simple and powerful .Finally , I/O message transmissions are accomplishe d in a record-oriented rather than a byteoriented fashion, so that high-speed I/ O devices can be efficiently connected .This construction has resulted in a twoto tour-told improvement in the aggregat e transmission rate and a much mor e efficient utilization of core storage .Although the primary implementatio n goal in the new RAMP system was increase d through p ut and flexibility as compared t o the old system, the development of the ne w system has been different enough from th e old that it is presented here in toto ; an d familiarity with the old system is no t assumed requisite in the exposition .