🚀 go-pugleaf

In a recent article jje@virtech.uucp (Jeremy J. Epstein) writes:

>What were the advantages/disadvantages of 7 track as opposed to
>9 track?
   Compatibility with existing tapes.  Beyond that, nothing.

>BTW, the 9 track drive had low, medium, and high densities in those
>days: 200 BPI, 556 BPI, and 800 BPI.  1600 and 6250 hadn't even
>been thought of...

   Nope.  The 200/556/800 BPI densities were for 7-track tape.  The 
   original 9-track tapes were all 800 bpi, with 1600 bpi and 6250
   arriving later.  One real advantage of specifying 9-track tape
   is that the tape drive senses the density of a tape automatically,
   so you don't have to specify the density when using a drive
   capable of more than one density.  Also, 9-track tape is *always*
   written in odd parity, so you don't have to specify that option.
   One real pain in 7-track days was having to be able to handle a
   tape with some records in even parity and some in odd.  At least
   I never had to work with a tape in more than one density...

Joe Morris