31 Dec
2015
31 Dec
'15
12:33 a.m.
Erik E. Fair scripsit:
Rather than memory-mapped I/O, the NOVA had I/O
instructions, and
six bits of device codes.
Same as the PDP-8, in fact. But all my PDP-8 work was with OS/8,
which runs with interrupts off: you can turn them on in userland if your
program wants to use them, but you have to shut them off before invoking
any system services. So I know little of these sixties sitcoms of
which you speak.
Since "page zero" of the NOVA (the first 256
words of RAM) was a
critical resource (direct reference from anywhere else in RAM rather
than using space-expensive indirect addressing, plus, there were some
autoincrement and autodecrement locations - reading them caused the
stored value to change - handy for counters and pointers),
All exactly like the PDP-8.
--
John Cowan http://www.ccil.org/~cowan cowan(a)ccil.org
You are a child of the universe no less than the trees and all other acyclic
graphs; you have a right to be here. --DeXiderata by Sean McGrath