Subject: Re: vibrating hard disk makes computer move
From: [email-masked] (James R Ebright)
Date: 10 Mar 1994 18:16:11 GMT
Newsgroups: alt.folklore.computers,alt.folklore.urban

In article <[email-masked]>,
Joe Landry <[email-masked]> wrote:
>Hello, world!
>
>A friend of mind who went to RPI told me the following urban legend.
>Long ago when computers were more primitive, some RPI students got a
>computer to rattle across the floor by making its hard disk resonante.
>They supposedly got the disk to resonant by doing disk accesses in a
>special way.  Sounds like bogatude to me.  Anybody know anything about 
>this?

It is true.  Old disks used a HUGE voice coil to move a HUGE actuator on
which the heads were mounted.  The mass being moved was a significant
percentage of the entire drive's mass and was located at the top of
the drive, making oscillations stronger.

A friend of mine was a NCR CE and found a certain diagnostic which
maximized head travel would cause drives to rock so much they would
sometimes fall over.

Occasionaly he would be called to a customer site to put a drive upright :)

(His fix was to epoxy an L-shaped bracket to the drive frame and the floor.
Not pretty...but it worked.)

-- 
 A/~~\A   'moo2u from osu'   Jim Ebright   e-mail: [email-masked]
((0  0))_______     "Education ought to foster the wish for truth,
  \  /    the  \     not the conviction that some particular creed
  (--)\   OSU  |     is the truth." -- Bertrand Russell

From: [email-masked] (Joe Morris)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer move
Date: 10 Mar 94 19:16:33 GMT

[email-masked] (Joe Landry) writes:

>A friend of mind who went to RPI told me the following urban legend.
>Long ago when computers were more primitive, some RPI students got a
>computer to rattle across the floor by making its hard disk resonante.
>They supposedly got the disk to resonant by doing disk accesses in a
>special way.  Sounds like bogatude to me.  Anybody know anything about 
>this?

Back in the late 60s or early 70s one of the IBM mainframe system programmers
at Florida State (or maybe UF) wrote a collection of instruction pages for
the various utilities installed on the computer there.  I'm sure that if
I spent a week or two I could find it, but from memory the following is
close to what you found on one page buried among other, legitimate
documentation pages:

NAME:      SEEK3330

FUNCTION:  To functionally destroy a 3330 disk drive

OPERATION: When started SEEK3330 issues a series of random SEEK commands
           to the selected disk.  While these SEEK commands are executing,
           at some point the head rack motion will be occurring at the
           resonant frequency of the cabinet in which the disk drive
           mechanism is mounted.  When this occurs the sympathetic vibration
           of the housing will cause the disk drive to walk out of the
           computer room under its own power.

JCL:       //jobname  JOB  <accounting information>
           //JOBLIB   DD   DSN=SYS1.UTILITY,DISP=SHR
           //STEP     EXEC PGM=SEEK3330,REGION=128
           //SYSUT1   DD   UNIT=xxx

           where:

             xxx is the device address of the disk to be destroyed.

RETCODE:   0  - The disk was successfully destroyed
           16 - The program was terminated before destruction was complete.

NOTE:      The use of SEEK3330 on Itel disks should be considered redunant.

(Me speaking again)

The "NOTE" at the end was the howler.  I strongly suspect that the shop
had experiences with that vendor which were less than pleasant.

Joe Morris / MITRE

From: [email-masked] (David S. Broudy)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer move
Date: 10 Mar 1994 21:02:57 GMT
 <jcmorris.763326993@mwunix>

Well, this isn't exactly a vibrating (exploding, more like) HD story,
but here goes:
One place I worked at had an Alpha Micro mini that had some Fujitsu
14" hard drives. One day we heard this horrendous screeching sound
coming from the computer room. We all ran in to see one of these
monsters losing its spindle bearings and basically sending the whole
disk stack through the casting at 3600 rpm. Yes, we ran. Pretty
spectacular...

---------
[email-masked]
"I wouldn't normally do this kind of thing"

Newsgroups: alt.folklore.urban,alt.folklore.computers
From: [email-masked] (Robert Bernecky)
Subject: Re: vibrating hard disk makes computer move
Date: 10 Mar 94 20:35:09 GMT

In article <[email-masked]> [email-masked] (James R Ebright) writes:
>In article <[email-masked]>,
>Joe Landry <[email-masked]> wrote:
>>Hello, world!
>>
>>A friend of mind who went to RPI told me the following urban legend.
>>Long ago when computers were more primitive, some RPI students got a
>>computer to rattle across the floor by making its hard disk resonante.
>>They supposedly got the disk to resonant by doing disk accesses in a
>>special way.  Sounds like bogatude to me.  Anybody know anything about 
>>this?
>
>It is true.  Old disks used a HUGE voice coil to move a HUGE actuator on
>which the heads were mounted.  The mass being moved was a significant
>percentage of the entire drive's mass and was located at the top of
>the drive, making oscillations stronger.
>

Those are the New Old disks.  The  OLD disks  used hydraulically
driven pistons  (oil) to move the heads across the drive.   The 
pump was driven  by the  same Very Large motor  (probably  one horse
or more)  which spun the disk. They  held a LOT of  data though:
IBM 2311's  held somewhere close to 20 megabytes, if memory serves.
(Memory may not be serving today, and my  manuals  are all  at home).

Besides having the nasty habit of leaking  oil all over the floor,
both these and the linear motor  voice coil machines  DID tend to
walk around a lot. Some of  those drives (Memorex or IBM, can't
remember  which) also liked to catch  fire. 

Bob

From: [email-masked] (Sarr J. Blumson)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer move
Date: 10 Mar 1994 22:28:12 GMT

In article <[email-masked]>,
[email-masked] (Joe Landry)
writes:
|> Hello, world!
|> 
|> A friend of mind who went to RPI told me the
|> following urban legend.
|> Long ago when computers were more primitive,
|> some RPI students got a
|> computer to rattle across the floor by making
|> its hard disk resonante.
|> They supposedly got the disk to resonant by
|> doing disk accesses in a
|> special way.  Sounds like bogatude to me. 
|> Anybody know anything about 
|> this?
|> 
This is true:

The General Electric DSU-250, which was 8 feet tall, had 16 (32?)
independently positionable arms and could be moving 7 of them at once, could
be made to walk around the room by careful seeking.  This is only one of the
reasons it never made it past prototype.

-- 
--------
Sarr Blumson                         [email-masked]
voice: +1 313 764 0253               home: +1 313 665 9591
CITI, University of Michigan, 519 W William, Ann Arbor, MI 48103-4943

From: [email-masked] (Joe Morris)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer move
Date: 11 Mar 94 00:35:00 GMT

[email-masked] (David S. Broudy) writes:

>Well, this isn't exactly a vibrating (exploding, more like) HD story,
>but here goes:
>One place I worked at had an Alpha Micro mini that had some Fujitsu
>14" hard drives. One day we heard this horrendous screeching sound
>coming from the computer room. We all ran in to see one of these
>monsters losing its spindle bearings and basically sending the whole
>disk stack through the casting at 3600 rpm. Yes, we ran. Pretty
>spectacular...

The early development of rotating memory devices at IBM was a somewhat
clandestine affair since it didn't have Upper Management approval.  One
of the late-development cycle boxes was similar to the eventual
1301 RAMAC product, with huge platters (30 inch diameter, give or take
30 years memory loss) with a single head which worked like the tone arm
on an old juke box, running up and down a guide, darting into the disk
stack as needed to read or write data.  The disk stack (How many?  That
number is completely gone) was mounted on a vertical axle perhaps 40 inches
high.  The disks were *massive*, especially by today's standards.

Yup, you guessed it.  One day the axle failed, sending high-tech Frisbees
all around the laboratory.  One of the workers got his scalp sliced by
a passing disk, but there were no other injuries.

And no, I wasn't there.  I can't testify that this isn't urban legend,
but I've seen occasional articles in professional journals which
refer to the events.  Formal citations and/or (truthful) there-I-was
stories are solicited.

Joe Morris / MITRE

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer move
Date: 11 Mar 1994 15:24:30 GMT

From article <[email-masked]>,
by [email-masked] (Joe Landry):
> 
> A friend of mind who went to RPI told me the following urban legend.
> Long ago when computers were more primitive, some RPI students got a
> computer to rattle across the floor by making its hard disk resonante.

Urban legend?  Far from it.  Back in the days when a disk drive was the
size of a top-loading washing machine (1970 to 1975, and you can buy
those old things surplus for a song these days), disk packs were 11
platters high, with 20 recording surfaces, with 400 tracks per surface,
and 8K bytes per track (that's 64 meg per drive, by the way), and moving
the head assembly in and out definitely could make the drive jump around
about the same way a washing machine does when on spin cycle with a
wadded up beach towel over on one side.

My favorite disk drive diagnostic was what I called the wobble test.
This would seek from track 200 to 199 to 201 to 198 to 202 to 197 to
(you get the idea) 399 to 000 and then work its way back up.  The test
would begin with an audio hum as the heads seeked back and forth between
adjacent tracks, but the frequency constantly fell until, in mid test,
it was more of a lub-lub-lub-lub noise as the whole drive shook, and then
the frequency would climb back into the audio range as it finished.

At some seek frequencies, even with the shock adsorbers inside the drive,
the whole thing would threaten to get up and walk, and it is clear that
careful programming to exploit those frequencies could make things happen.

By the way, those disks were hardly monsters by the standards of only a
decade earlier.  They were the paragon of miniaturization.  In the
early 1960's, bryant was making multiple surface disk drives with
platters 4 feet in diameter!
					Doug Jones
					[email-masked]

Newsgroups: alt.folklore.computers,alt.folklore.urban
From: [email-masked] (Articulate Mandible)
Subject: Re: vibrating hard disk makes computer move
Date: Fri, 11 Mar 1994 18:03:42 GMT

It's twoo! It's twoo! Some disk access patterns can indeed make some types
of disk drives induce enough motion in their cabinets to cause said
cabinets to walk across the floor. Here's an eyewitness account.

Take a typical 60 inch high 19 inch rack cabinet with a pair of DEC RK05
cartridge drives mounted as high as they can go. Attach said pair of drives
to a DEC PDP-11/10. Run DEC's oscillating seek diagnostic on both drives.
Adjust the inner and outer cylinder limits on both drives until the cabinet
does indeed start creeping.

That's what I'd do with that configuration whenever I was bored and there
was nothing corporately useful for the machine to do.

From: [email-masked] (Simon Slavin)
Newsgroups: alt.folklore.computers,alt.folklore.urban
Subject: Re: vibrating hard disk makes computer mov
Date: 12 Mar 94 13:59:04 GMT
Followup-To: alt.folklore.computers

In article [email-masked], [email-masked] (Tracy R. Reed) writes:
>: The General Electric DSU-250, which was 8 feet tall, had 16 (32?)
>: independently positionable arms and could be moving 7 of them at once, could
>: be made to walk around the room by careful seeking.  This is only one of the
>: reasons it never made it past prototype.
>
>This vibration surely destroyed the device, right?

I've seen it done on a production model attached to an in-use DEC 10, running
TOPS 10.  It walked.  It was fine afterwards.  It didn't destroy the disk (but
the operator who showed me *had* mounted a scratch disk.).  Each swing was
about two to three inches.  I was larval and have no idea of the make/model.

Vibration destroying devices ?  Naah.  These were the days of armour-plated
peripherals.  Anyone remember the ASR-34 ?  Commonly described as an armoured
tank adapted for I/O work.  Telex machine + teletype in one box, and took
three people to lift it safely.

Simon.
---
< "So I told her a couple of white lies, like I have friends and a life ..." >
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