[FoRK] DEC in the past

Marty Halvorson marty at halvorson.us
Fri Jul 26 17:48:49 PDT 2013


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


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