help reading 9 track tape

Paul Koning paulkoning at
Thu Mar 24 19:13:11 CDT 2016

> On Mar 24, 2016, at 5:40 PM, Jecel Assumpcao Jr. <jecel at> wrote:
> Jon Elson wrote on Thu, 24 Mar 2016 10:34:48 -0500:
>> What density and format is this tape?  Not all drives 
>> support all densities.
> I actually mentioned this detail to his advisor when they were
> discussing this topic after his student's defense, but I don't think he
> remembers this information. I am guessing that the tape was recorded
> around 1986, so any new density introduced after that (if there were
> any) can be ruled out. About the format, I have no idea.

Standard half inch tape was around well before that, I don't think anything changed for some years before.  Standard densities are 800, 1600, and 6250 BPI.  Hopefully it's not one of the oddball values that a few benighted manufacturers implemented, like 3200 BPI.

7 track, as Nico points out, is harder to find.  It stayed around longer than the 1960s, especially on some architectures.  For example, around CDC mainframes  you're far more likely to find it than, say, on PDP11s (though DEC did sell 7 track drives for the PDP11).  7-track standard densities are 200, 556, and 800 bpi.  There still are people around with working 7 track drives, so if you have that, there is still an answer, but the number of them is certainly more limited.


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