Help reading a 9 track tape

Jay Jaeger cube1 at
Fri Aug 6 11:45:55 CDT 2021

On 8/5/2021 2:57 PM, Len Shustek via cctalk wrote:
>  > On Aug 5, 2021, at 8:39 AM, Jay Jaeger via cctech 
> <cctech at> wrote:
>  > I know Paul well (we were contemporaries at U. WI).  He does not do 
> that very often.  He did not indicate any issue with a fire at the 
> building that contains his collection when I last spoke with him.
>  >
>  > He does not actually read "blocks".  He reads the tape in an *analog* 
> fashion, and then processes the results with software.  That is how he 
> recovered the IBM 1410 system tapes and diagnostics, for example.
>  >
>  > To be honest, I doubt that this content would be such that he would 
> be likely to volunteer.
> Some years ago, inspired by Paul Pierce's earlier program in Java, I 
> wrote similar software in C to decode the analog waveforms from tapes in 
> a variety of formats: 7-track NRZI, 9-track NRZI, PE, and 6250 BPI GCR, 
> and 6-track NRZI for Whirlwind.


For completeness, here is a link to Paul's 7 track recovery software 
info (which is what I believe you are referring to - there is also an 
older version.)

> As a one-time physics major, I *am* interested in the Schoonschip 
> content. I've offered to James Liu to give it a go if he can't get 
> someone like Chuck to read it in a more straightforward fashion.

There is also this one for 9 track drives:

(There is an article out on the 'net that points to this project, 
referencing use of a logic analyzer to capture the data, but today I am 
having trouble finding it with my searching spells.)


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