Then either the engineer was pulling my leg or he was simply wrong in 
his conjecture.

Anyway, new thread starting. New Subject Line.

Walter J. Murray wrote:
> Tracy Johnson wrote:
> 
>> I'm reminded once an Engineer told me a 1600bpi "only" drive could
>> theoretically read 800bpi written tapes.  The procedure was to force
> the
>> machine to only read every other bit.  All one had to do was discard
> the
>> checksum at the end.
> 
> That's a good one!  :-)
> 
> As I recall, the drives always used NRZI (Non-Return to Zero, Inverted)
> encoding for 800 bpi, and PE (Phase Encoding) for 1600 bpi.  With NRZI,
> tapes were written with odd parity, so that each frame would have at
> least one 1-bit.  (Otherwise, a string of NUL characters would look like
> a section of unrecorded tape.)  With PE, I think even parity was
> generally used.  
> 
> I'm skeptical that a drive designed for PE would be able to make any
> sense of an NRZI-encoded tape.
> 
> Walter  
> 
> Walter J. Murray


-- 
BT

Tracy Johnson
Justin Thyme Productions
Ye olde free telnet games at:
http://hp3000.empireclassic.com/







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