DECDLD usage -good enough for minimal graphics?

Paul Koning pkoning at
Mon Aug 8 16:51:06 CDT 2005

>>>>> "Julian" == Julian Wolfe <Wolfe> writes:

 Julian> Hello everyone!  I was just investigating the usage of DECDLD
 Julian> for defining a small graphic screen on my PDP11 during a
 Julian> program.

 Julian> When using a VT220 at 19200 baud, how fast can a screen be
 Julian> refreshed using DECDLD graphics?  I was thinking of doing a
 Julian> multiplayer (4 player) game using this system.

If you plan the graphics properly, sure, no problem.  PLATO had
multiplayer games long ago using 1200 baud lines.  That was with a
MUCH more efficient graphics encoding, though.

Did you mean VT240?  Unless my brain is going, VT220 is text only.
VT240 supports REGIS, which is a simple graphics protocol (somewhat
verbose in its encoding as I recall).

Assuming that REGIS doesn't lose more than a factor of 16 in coding
efficiency vs. PLATO -- which should be true -- you should be able to
get a couple of refreshes per second.  There are plenty of interactive
games that can live with that.


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