> The 9-track tapes of slightly later vintage were 
> 800 or 1600 bpi; in the mid-1970s, as I recall, those were succeeded by 
> 6250 bpi tapes.

Reminds me of some tapes we used for data interchange between a pdp11
and a Univac mainframe [1].  Occasionally they would be put into the wrong
drive on the mainframe and written with 6250 bpi 'phase encoded' data.
Our pdp11 would still read the 800bpi NRZ data....

	David

[1] 6 bit characters in an EBCDIC like set and 36bit words written to
9 track (ie 8 data bit) tape.  Two 36bit words covered 9 'bytes' on tape.
Fortunately the characters were in the correct order on tape!

-- 
David Laight: david@l8s.co.uk