rick@pavlov.bcm.tmc.edu (Richard H. Miller) (02/11/89)
[This may be a duplicate but it looks like the first attempt did not post last
night]
I am not sure of exactly when it appeared, but the UNISYS 1100's have had the
concept of a fork to start another activity for a long time. The ER (executive
request) is octal 13 which indicates it is one of the early ER's in EXEC-8. If
I remember correctly, the fork$ ER will start up another activity with its own
switchlist and own register set. This activity may be selected for processing
by the processor whenever required as is asynchronous w.r.t the mother process.
In basic mode machines, the user may select the new activity to run with the
major register set (all user registers) or the minor set (a subset of the
registers with the other registers in an undetermined state.) The new process
can set up its own banking scheme and base other banks than what the mother
process has based. It still uses the same memory map as the other processes
for the run.
In the newest level of EXEC-8 an activity has the ability to have a local set
of bank descriptors which apply ONLY to that activity.
Richard H. Miller Email: rick@bcm.tmc.edu
Asst. Dir. for Technical Support Voice: (713)798-3532
Baylor College of Medicine US Mail: One Baylor Plaza, 302H
Houston, Texas 77030