[wplug] degaussing tapes and hard drives

[Burt E Reany]

   For many of these media, the starting point for data on the tape is
created as a special data block written (yrmv) cm. from the physical start
of the tape. (This used to be determined by a reflective patch physically
glued on the backside of the tape in the 9-track reel-to-reel days - a
"Reflector Spot"). (In earlier days, some vendors drives would only work
with their pre-formatted cartridges, where their shop had written this
control data block to the tapes before they left the factory). In these
cases, degaussing erased the control blocks so that the drives couldn't
even find the start of the tape - and you got no software that could
recreate that control block.
   This was described as a feature.


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