Polymorphic System88 disk

Chuck Guzis cclist at sydex.com
Tue Apr 8 13:06:11 CDT 2008

> Date: Tue, 8 Apr 2008 05:59:37 -0700
> From: dwight elvey 

Will all respect for your efforts, Dwight, at least you knew the 
origin of the diskette and had a faint idea of what might be on them.

You haven't lived until someone shoots you a bunch of diskettes with 
everything being unknown--the modulation technique, the code 
representation, the data rate or track spacing or byte width, much 
less the file system.

Your Polymorphics floppies sound a lot like a bunch of diskettes I 
got in recently from a manufacturer's in-house PCB stuffing robot.  
The format appears to be a "roll your own".

It's hard to say which is the most fun--diskettes discovered to be 
GCR where you have no idea of what the group size is, nor what the 
groups correspond to.  Or diskettes written on something like a 
typewriter where the code's not ASCII, nor does A immediately precede 
B--and you have nothing that says "this is a printout of what's on 
the diskette".

Hint:  You start with a statistical analysis of the pulse stream and 
go from there.

For me, it's a lot of fun, ferreting out things by bits and pieces 
until the big picture emerges.


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