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Article #488

Re: TRS-80/PDP-8 radio fun

#488
From: je... Randell Jesup
Date: Mon, 18 Dec 1989 11:19
37 lines
2810 bytes
There was an old PDP-8 at RPI owned by the XRay crystallography lab, which was
donated to the RPI-ACM in ~1983.  This was serial #165, had NO integrated
circuits in it (built entirely from DEC Flip-Chips - discrete transistors and
resistors, etc; about 4 flip-flops/board).  Anyway, it had an entire extra
cabinet of custom Flip-Chip hardware to control the Xray equipment.  What we
couldn't figure out was the speaker sitting on top of the bix, with a wire
running into it.  Well, we traced the wire back to a few extra boards which
implemented an i/o port, and sent the output bit through a pulse-amplifier
Flip-Chip to the speaker.  There were some card decks labelled with various
songs that came with it.  Cute hack by someone lost in prehistory.

Another amusing RPI hack involved MTS (mentioned before).  There were NO
inter-process communication facilities at the time, and someone wanted to
write a 'talk' program.  This person noted that the fp-registers of the
machine (IBM 3033) were stored in readable shared memory (if I remember right)
when your process was not running.  So he passed messages in the FP registers,
by stuffing them and then doing a wait of some sort.

Of course, MTS also had a standard PDP-8 simulator...

Last story: Some of the Courier terminals (3270-workalikes) had their
controllers left in maintenance mode.  You could access some strange functions
(most of them useless) by playing with funny combinations of function keys.
One of them displayed the current packet being sent to all the terminals (to
update a screen).  An ACM member playing with this saw someone's editor screen.
Said screen had a message to the systems staff about people being able to read
other peoples screens.  The controller was fixed soon after that. (The ACM
people were really hunting for a fabled "asteroids" program buried in the
terminals.  There wasn't one, but they disassembled much of the operating code
in the terminal by hand in the process of looking for it (Z80-based machine)).

Does any one else remember the infamous "Charlie Roth clones"?

-- 
Randell Jesup, Keeper of AmigaDos, Commodore Engineering.
{uunet|rutgers}!cbmvax!jesup, je...@cbmvax.cbm.commodore.com  BIX: rjesup  
Common phrase heard at Amiga Devcon '89: "It's in there!"
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From: je...@cbmvax.commodore.com (Randell Jesup)
Newsgroups: alt.folklore.computers
Subject: Re: TRS-80/PDP-8 radio fun
Message-ID: <9078@cbmvax.commodore.com>
Date: 18 Dec 89 11:19:42 GMT
Reply-To: je...@cbmvax.commodore.com (Randell Jesup)
Organization: Commodore, West Chester, PA
Lines: 37
Posted: Mon Dec 18 12:19:42 1989
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