Subject: Re: Looking for computer tales

From: [email-masked] (alley cat)
Date: 6 May 1993 23:12:32 -0400

...i'd be happy to relate two stories from my high school days, where
we had a PDP-8/e...

You've heard (or read, perhaps in the jargon file) about `walking
the drives' of computers?  ...well, some call it a myth, but i *did*
it, and i have witnesses (Larry Kolodney, where are you?)...in
retrospect, it was a foolish thing to do -- i could have done serious
physical damage to the system...but i was a kid, and after hearing
what the effects would be, i just *had* to try it...

...i didn't know enough assembler (PL-1?) to access the RK05j disk
directly, so i programmed a BASIC kludge to sort of simulate what i
wanted; i wrote two BASIC programs, one called A.BAT and one called
B.BAT, each of which consisted of a single line -- A.BAT contained the
line CHAIN B.BAT and B.BAT contained the line (you guessed it!)
CHAIN A.BAT (what do you want, alt.hackers material?  ...i was a
neophyte!)...i then did some manipulation so that a DIR command
indicated that these files were fairly far apart from each other, and
let her rip...

...what followed was *exciting*...the first thing i noticed was that
the disk access light on the front panel, which generally flickered a
few times once in a while, was a blur of action...then, as the quickly
vibrating read/write arm set up sympathetic vibrations in the cabinet,
the whole thing began to shake...gently at first, but then to a far
greater degree (almost like an off-balance washing machine)...i'm not
sure the cabinet actually moved from its location on the floor, but it
was damn near ready...

...and at that moment, Mr. Mezzadri, who was in charge of the
computer, walked into the computer room, noticed the computer sounded
*strange*, saw the disk access light freaking out, and *ran* for the
on/off switch with key in hand...he was incredibly pissed off, knew
exactly who was responsible (Larry and i were basically the only
people in the whole school, Mezzadri included, who knew how to pull
stunts like this), but somehow i got into virtually no trouble...

...well, maybe after that story the next will seem somewhat
anticlimactic, but what the hell, it brings back fond memories...

...Larry & i used to have contests of all kinds, mostly `beat each
other to the front of the class with the first correct program' type
of thing...we devised a contest to see who could come up with more
ways to crash the system, but it eventually became a mutual
project...here's some of the ways i remember:

1) The easiest: We had a mark-sense card reader; the BASIC command to
   read cards from it was CDR...if you typed CDR & forgot to turn the
   card-reader on (or if you purposely turned it off first ;) the
   system would grind to a halt *instantly*  :O

2) You could easily overflow the interrupt stack with CTL-C's...one
   way was to just lean on the CTL-C button; another was to make
   a punched paper-tape consisting of a series of CTL-C's & feeding
   it into the ASR-33...

...hmmm, i don't seem to remember any others off-hand...so how did
y'all spend *your* high school days?  :)
						-allen

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sometimes you have to look reality right in the eye.......and deny it!
                                                         -Garrison Keillor
allen lutins          [email-masked]

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From: [email-masked] (Charles Lasner)
Date: Fri, 7 May 1993 03:54:08 GMT

>...i'd be happy to relate two stories from my high school days, where

Which is programmed in PAL, not PL-1.

Rocking machines, including -8's has been done a few times.  You can really
get an RK05 to shake, and using overlapped seek operations, you can get
it *really* shaking if you have multiple drives.

I have written a diagnostic for the SCSI disks on the 8/e-8/a which tries
all of the possibly rock-seek sequences deliberately to find "resonances"
in the system that make it flunk, etc.  You can include up to four
simultaneous drives in the test (hardware limitation).  I once started the
test up, and it eventually failed!  (It turned out that it overloaded the
PC-type switching power supply.  Using a bigger supply made it work fine
again.)  Even these little MFM drives can shake up a mean storm when mounted
in the H960 cabinets.  Apparently, the cabs are just loose enough to get a
real shake going if you hit the correct rate, etc.

On a slightly different subject, I was privileged to go to the taping of
the demo videotaping of a tentative TV quiz show called The Computer Game.
It started with the opening shot of the PDP-8/e front panel, which was 
identified as "Mini" the mini-computer.  The host was (Dandy) Dan Daniels,
(somewhat) famous radio/TV personality/disk-jockey.  Fake contestants were
played by well-known faces, i.e. people who's name you don't know, but you
see all the time - TV commercial actors.

The 8/e had two RK05's, and the producers wanted it to move somehow in a 
way that the audience could see.  But no effect could be accomplished with
the disks that was acceptable.

Eventually, they solved the problem a little differently: there were also
a pair of TU56 drives on a TD8E on the machine as well.  They applied black
plastic electrical tape to the front of the reels of the DECtapes, and then
on queue, the tape was rocked back and forth a few times in sync with some
pre-recorded music.  The whole thing did look rather cute, etc.

The contestants were to "challenge" the -8 to some kind of word game.  The
machine couldn't lose; the entire dictionary was available as a file.  They
were going to "handicap" the -8 somehow if the show was picked up, so that
contestants might have a ghost of a chance of winning, etc.

The show was never picked up by the network (CBS).  I still have the
ticket to the show as a memento.

cj "Won't apply electrical tape to DECtape reels for food" l

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From: [email-masked] (Joe Vigneau)
Date: Fri, 7 May 1993 12:57:54 GMT

>y'all spend *your* high school days?  :)

     I'm using to read this newsgroup!
-- 
   / _   __    /  [email-masked]
<_/ <_> <-'   /  WPI - Class of '97 - Computer Science

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From: [email-masked] (DoN. Nichols)
Date: Sun, 9 May 1993 02:53:02 GMT

>...i'd be happy to relate two stories from my high school days, where

	[ ... ]

>y'all spend *your* high school days?  :)

	Well ... Since my high school days ended in 1960, I really didn't
have access to computers, so I was attempting to design (and collecting
parts for) a liquid-fueled rocket.  Luckily, I didn't have access to some of
the fabrication methods that I determined that I needed, so it never got
built (or exploded. :-)

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From: [email-masked] (Randell Jesup)
Date: 10 May 93 02:44:38 GMT

>y'all spend *your* high school days?  :)

	I was one of 3 or 4 students with keys to the room with the '8/e
(12K, dual dectapes, 3 asr33's).  Basically, we owned the room, no one else
used the machine.  Other than writing games in edubasic, using it to do our
pv=nrt chem homework, and just generally hanging out there whenever we weren't
in class, we pulled a few pranks.  One was to use the asr33's with a paper
tape loop to print football pool forms.  I still have 8 or so dectapes and
several racks of fan-fold paper-tape software.  Life patterns were another
popular diversion (a hint: don't play with Life when your only output is
an asr-33...)

-- 
GNU Emacs is a LISP operating system disguised as a word processor.
 - Doug Mohney, in comp.arch

Randell Jesup, Jack-of-quite-a-few-trades, Commodore Engineering.
[email-masked] or rutgers!cbmvax!jesup	BIX: rjesup  
Disclaimer: Nothing I say is anything other than my personal opinion.

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From: [email-masked]
Date: 10 May 93 13:43:17 +0930

> pre-recorded music.  The whole thing did look rather cute, etc.

Dectape motion is interesting.  On the pdp8, they rock back and forth, but on 
a pdp11 they zipped along because the blocks were interleaved (4 to 1 ?).
We had a program called PIP11 which ran on a pdp8, and could read/write pdp11 
formatted tapes.  Doing a transfer between an 11 format tape and an 8 format 
tape caused one drive to rock furiously while the other calmly zipped along.

Regards,

John Bennett                                   [email-masked]

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From: [email-masked] (Charles Lasner)
Date: Tue, 11 May 1993 00:29:18 GMT

>popular diversion (a hint: don't play with Life when your only output is

If you are offering, I can read all of that media for you.  Perhaps some of
it is also interesting to our readers, etc.

cjl

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From: [email-masked] (Charles Lasner)
Date: Tue, 11 May 1993 00:37:02 GMT

>tape caused one drive to rock furiously while the other calmly zipped along.

The layout of DOS-11 and related systems is that they interleave by two
actually.  You transfer a block, skip the next, and usually are able to
transfer the next one in the same direction, since you can restart the
tape search process and find what you want skipping over only a single block.

The PDP-8 DECtape copy program uses this method:

First, after determining the block size of the tapes, read forward without
ever turning around.  A bunch of blocks are read into memory.  Then, they are
written onto the other tape.  Then, the equivalent number of blocks are ignored
and you transfer the same number into memory.  Since it doesn't take too many
blocks to search at full speed, this can be done forward again.  The data
is then written forward to the target tape, and the same logic applies.  Thus
when you get to the end of the tape, both tapes are positioned at the end, and
half of the tape is copied, and the rest is a bunch of gaps.  Then the whole
process is done in reverse, since the data is read reverse and then written
reverse (done this way it's direction independent).  When the tapes are again
at the beginning, the tape is totally copied.

All of this can be run in a basic 4K -8 with a pair of TU55 or TU56 drives and
a TC01/08 controller.

cjl

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From: [email-masked] (Charles Green)
Date: Tue, 11 May 93 01:59:36 GMT

[email-masked] (Randell Jesup) writes:
>(a hint: don't play with Life when your only output is an asr-33...)

Sez yew!

A program I wrote years ago for my TI-58C calculator does a 10x10 Life matrix
and outputs it on the attached printer.  (A few minutes per generation, as I
recall... :-)

-- 
Charles Green			"The...fireworks...have just...begun!"
[email-masked]					-Captain Zilog
signature virus 2.1c - Copy me into your .signature if you love Jesus!

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From: [email-masked] (Bernd Felsche)
Date: Wed, 12 May 93 04:25:50 GMT

>popular diversion (a hint: don't play with Life when your only output is

Did you ever set the bell on the `33 to ring like a phone? A really
silly prank if it does so at night, just as the night watchman's out
in the corridor, hears a phone ring in the locked room, unlocks the
room as the bell stops, and then goes to search in vain for a
non-existent phone.

It only works 2 or three times... :-)
-- 
+-----+ Bernd Felsche                     _-,_|\  #include <std/disclaimer.h>
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From: [email-masked] (gordon hlavenka)
Date: Wed, 12 May 1993 15:41:59 GMT

>(a hint: don't play with Life when your only output is an asr-33...)

When I was in high school (class of '76) we programmed Life using an
8 X n matrix, with the output on paper tape from an ASR33...

We also had an 80 X 80 Life which outputted to paper on the ASR33.
SSSSLLLLOOOOWWWW!

And, a hexagonal Life.  The actual grid was a one-sixth wedge of a
hexagon.  After the generation was calculated, six duplicates of it
were printed out (on that poor ASR33 again :-).  Pretty snowflakes.

Final ASR33 trick:  AC / MQ movies.  Dirt simple little program that
was toggled into the front panel of the 8/e.  Displayed the 8 (for AC)
or 12 (for MQ) bits read from the tape, then repeated.  By laboriously
punching tapes, we could produce little one-dimensional movies.  Very
minimalist art :-)  Sometimes we'd even have narration.  Chase scenes,
love stories, all seven plots.

Those were the days!

-- 
----------------------------------------------------
Gordon S. Hlavenka           [email-masked]
Vote straight ticket Procrastination party Dec. 3rd!