berger@clio.las.uiuc.edu (07/12/88)
The video glitching you see ("snow" usually refers to a weak received
signal on a television) is the result of updating the memory during an
active video interval. This is inherent to the design of many video
display circuits, and is not limited to the CGA or the IBM world in
general.
As you may have noticed with a CGA, many programs blank the screen
while updating (IBM calls this "flicker"), which eliminates the glitching
but slows down the display, and causes the flickering effect.
If your display has a register to tell you when it's in a blanking
interval, you can read the register and update the screen memory at
that time. You can also use the "flicker" technique, though I
personally find that more annoying than the glitching.
Mike Berger
Department of Statistics
Science, Technology, and Society
University of Illinois
berger@clio.las.uiuc.edu
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