On 2018-08-02 02:26, dave porter wrote:
Not really a simh question, but this might be an appropriate
bunch of people. What actually used MARK on PDP-11?
I think I recall that some Fortran system (F4P?) used it,
but that's a vague feeling at most.
Certainly as a Macro-11 kernel-mode weenie, I never
felt the need.
As far as I know, nothing used MARK.
It's ugly in that it requires that I-space and D-space overlap, at least
for the stack, for it to work.
I once heard a rumor that DEC only came up with it to extend some
copyright or patent a few more years, but I'm not sure there is much
truth in that.
Anyway, it was an attempt at having a return mechanism for routines that
cleaned up the stack, in a time where you did not have a frame pointer.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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