Secrets of the Symbolics Console: Part 1

The machine does indeed power up and run:

genera hello

But this is not enough.

The console is a museum piece. While a Lisp Machine circa 1986 might last for a reasonably long time between repairs, a CRT of the same vintage likely will not. Moreover, it is a pain to have around, even if it were indestructible. Wouldn’t it be nice to have a box which replaces the monstrosity entirely, with jacks to connect a standard VGA monitor, PS/2 mouse, and the beautiful Symbolics keyboard?

This promises to be less than trivial, however.

Here is what we find inside the console:

console top

Let’s examine the console cable:

1.  XMIT- Digital Audio serial data from system to the console
2.  XMIT+ Digital Audio serial data from system to the console
3.  TXD-  Biphase serial from system to console (console serial port)
4.  TXD+  Biphase serial from system to console (console serial port)
5.  RXD-  Biphase serial data from console to system (keyboard)
6.  RXD+  Biphase serial data from console to system (keyboard)
7.  RCV-  Audio Clock
8.  RCV+  Audio Clock
9.  Phase Encoded Video
10.  Video Ground
11.  Serial Ground
12.  Ground
(source)

Hmm, “Phase Encoded Video.”
The single extant repair manual tells us (p. 94-95) where to find the decoder board:

console side

The computational equivalent of three or four Commodore-64 machines languishes here.  There is even a set of debugging toggles and associated LED indicators.  One toggle is labeled “RUN/STOP.”

A closer look at the Phase Encoded Video decoder daughterboard:

So what is “Phase Encoded Video”?  Just another name for Manchester encoding, apparently.
And what does it look like?

My puny 275MHz non-storage scope (circa 1979) groans:

wave

To be continued…

This entry was written by Stanislav , posted on Tuesday September 01 2009 , filed under Distractions, Hardware, LispMachine, NonLoper, SoftwareArchaeology, Symbolics . Bookmark the permalink . Post a comment below or leave a trackback: Trackback URL.

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