24 Jan
2014
24 Jan
'14
9:50 a.m.
On Jan 24, 2014, at 12:14 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 01/24/2014 08:03 AM, Paul Koning wrote:
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.
Details are in CERL technical report X-26, available on Bitsavers (under
pdf/univOfIllinoisUrbana/plato/X-20_The_Plato_IV_Architecture_May72.pdf)
paul
Almost always that is true. There is at least
one oddball exception:
the 21-bit synchronous output stream for the PLATO terminals. That
consists of a start bit, 19 data bits, and a parity bit. Idling is
done by sending NOP commands, which have all zero in the data bits
(but the standard start and parity bits).
Heh, CDC could be very strange at times.