Direct ECS access

The CDC 6400 hardware has a base and bounds register which controls access to ECS (in addition to similar base and bounds registers for CM). In the system as implemented, the ECS bound was always set to zero while user code was running. After solving some minor bookkeeping problems, we could have given a subprocess direct access to a single file data block through this single base bounds pair. Thus the cost for each ECS file access to such a data block would be reduced from about 300 microseconds to about 3 microseconds.