... In SCOPE, PP # 10 was dedicated to this purpose - Each time shared PP (using a common adder) had its own memory of 4 K 12 bit words. This reduced the traffic to main memory. PP # 1 was normally assigned to monitor requests from the jobs assigned to "control points". A job would place a request in its relative memory location 0 for service by the system. PP # 1 would monitor these requests and assign other PPs to do the work, causing a PP to load a new program if necessary. I worked in CDC Special Systems from 1966 to 1971 - We shipped a version of SCOPE modified to run "Time Critical" which used modified code in PP #1 to guarantee user choice of - analog and discrete inputs - x milliseconds CPU time - analog and discrete output on a guaranteed time cycle - This was the best in the world at the time for doing hybrid computing :-)) which unfortunately was on its way out :-(( A system program to calculate resources to see if a new "time critical" user could be added to the running list. Yes :-)) Not in any system we shipped, and we could run the "EYE" and Northwestern University CHESS program with another PP displaying the chess pieces in nice form on the right hand scope. The left hand scope being assigned to monitoring activity at the normally 8 "control points", showing activity and requests for operator intervention such as mounting/removing tapes and printer(s) out of paper... Each PP had a 100 nano-second time sharing of the adder each 1 microsecond - hence a relatively hard upper limit of 10 PPs with out a special order for another 10 ( for customers such as Boeing). On later 6x00-series systems, such as the CYBER-73, the PPUs Greg Mansfield had KRONOS going, and shipping to some customers, - mostly educational - by the time I left. Greg was kind of a one man band - a bit of a Dilbert - a remarkably imaginative and productive individual - I left CDC long before the CYBER-73 .... Ed Thelen