full-disclosure - Re: DOS all platforms

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From: Valdis.Kletnieks at vt.edu (Valdis.Kletnieks@...edu)
Subject: Re: DOS all platforms 

On Sat, 24 Jan 2004 11:56:17 EST, "Jonathan A. Zdziarski" said:
> I heard of a bet going between a student and IBM many many years ago to
> write a virus to cause physical damage.  Apparently the student was able
> to use harmonic resonance and the hard disk drive to physically shake
> the PC off the desk.  

This story (and variants) dates back to the IBM2314 disk drive, if not further.

The problem with using "harmonic resonance" is that you have to first find a
resonant frequency.  Having done that, you need to be able to supply more
energy each cycle than is being damped out of the system.  So ask yourself - is
any desk you use bouncy enough so that if something approximately the weight of
a pencil (yes, that's how light the heads on a drive that will fit on a desk
are) was dropped on it, the desk bounced enough to matter?  Add in the fact
that the machine is probably sitting on little rubber feet precisely to damp
the vibration, and the difficulty in having things bounce that much and not
crash the heads....

Shake the desk enough to make a pencil roll off - probably doable.  Enough to
make a 30 pound computer walk off the edge? Doubtful.

I'd be more inclined to believe the 2314 variant - it was a disk drive from the
mid 60s, 10 platters, 14" no less, a data capacity of 29 megabytes.  Oh, and it
only did like 3600 RPM and min seek times were in the 50-75ms range (and
full-stroke seeks took a lot longer).  As a result, you had a lot more mass in
the arm assembly, and the full inside-to-outside cycle was down nearer to 100hz
where it might conceivably do something useful.
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