24 Jan
2014
24 Jan
'14
10:39 a.m.
True, but this particular system wasn?t a CDC
invention. It was
created at the University of Illinois, the inventors of PLATO. It?s
part of the amazingly clever I/O setup that connected to 1008
terminals via a single multiplexer device (TDM, one bit to each
terminal every 1/60th second). It uses a microwave TV link to
broadcast terminal output around the campus; the mux output was
cleverly encoded to look enough like a standard (analog, US standard
b/w) TV signal that a stock transmitter would happily transmit it.
I'm familiar with PLATO (at least the plasma display types; CRT versions
were after my time). The Sunnyvale PLATO contingent were just down the
hall--and numerous PLATO courses were offered in-company. I wasted lots
of company time playing AIRFIGHT myself and managed to gather a crowd
playing it in the CDC booth at (IIRC) the 1978 NCC, even though I wasn't
working for CDC at the time.
But even the old INTERCOM linkup used oddball data rates (2000 bps seems
to stick in my mind). Display code, not ASCII , of course.
--Chuck