🚀 go-pugleaf

In article <4341@mwk.uucp> gleason@mwk.uucp (Lee K. Gleason, Control-G Consultants) writes:
>
>  An early time sharing computer took advantage of the architecture of
>the machine it was running on to efficiently shuffle programs in core,
>but it could only do it to lower addresses. As time went by and more
>programs entered and exited, someone would get into a state where
>his process could shuffle no lower. The error message would tell 
>the user "30K of memory available - but not for you."

That would have been the PDP-6, the prototype for the PDP-10, circa 1964;
in his talk for DECUS, Peter J Hurley describes the situation thus:

    Since there was no swapping, everything had to fit in memory.
    Programs were shuffled to close up the unused space.  But because
    the BLT [BLock Transfer] instruction was used, shuffling could
    only move programs toward lower addresses (5K monitor, remember?).
    Thus, after one's compile had been running for twenty minutes,
    growing towards someone else's job, one might get an error message

	Core available, but not to you

    and could try to persuade the other person to kill his job or,
    more likely, would have to kill one's own job, type CORE 0 to
    cause shuffling, and start again.

Actually, it wasn't quite that bad, since one could, if the program
was reasonably well-behaved, CTRL/C it and SAVE the image before
forcing a core shuffle, and then restart the saved image afterwards.

Another good one is described in the same talk:

    PIP was invented by "Dit" Morse as a demonstration of device
    independence.  Its original name was ATLATL, which stood for
    "Anything, Lord, to Anything, Lord".  This was appropriate, as it
    took a certain amount of prayer to get anything to move between
    media.  In those days, when TTY's had backarrows (instead of
    underscores) that key was used instead of the equals sign in PIP.
    This, it was felt, was sufficiently obvious that anyone who, for
    example, tried to read from the line printer got a message like:

	You gnerd, device LPT: can't do input!

    That message was changed the day after Ken Olsen tried out ATLATL.

Lum
--
-- 
Lum Johnson      l...@cis.ohio-state.edu      l...@osu-20.ircc.ohio-state.edu
"You got it kid -- the large print giveth and the small print taketh away."
-------