[FoRK] DEC in the past

Ken Meltsner meltsner at alum.mit.edu
Fri Jul 26 18:29:52 PDT 2013


On Fri, Jul 26, 2013 at 7:48 PM, Marty Halvorson <marty at halvorson.us> wrote:

> Bill Kearney Wrote:
> "You kids, being able to build graphic interfaces without worrying about
> trying to get things done during the vertical refresh"
>
> Kids yeah.  I also worked at CDC on the 7600.  It was my code that had to
> refresh the main display console (a stroke display) on the fly and answer
> OS calls during vertical refresh from up to 15 separate processors, and the
> clock cycle was IIRC 0.1 micro-seconds.  And I had 2K of 12 bit words to do
> it in.  For those to young to remember a stroke display moved a beam of
> electrons around the screen based on 12 bit numbers, one bit of which was
> used to turn the beam on and off, the other bits were x and y coordinates.
>  Wherever the beam landed it illuminated a small dot of the screen.  So to
> write a character you had to send some number of words for each character.
>  Get it wrong and the display was unreadable, go to slow and the display
> flickered badly, go to fast and the characters weren't up long enough to
> read 'cause they'd be overwritten.
>
> It was fun though.
> Marty
>
> Highly cool -- I remember the CDC customer engineers playing a vector
graphics baseball game on the Lawrence Berkeley Lab CDC 6600 (IIRC)
console.  Amazing hack given that it was just something to do while
diagnostics were running.

Ken


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