CDC 9429 Floppy maintenance manual

Eric Smith spacewar at
Sun May 8 00:17:50 CDT 2016

On Sat, May 7, 2016 at 1:19 PM, Seth Morabito <lists at> wrote:
> I have reason to believe that the CDC 9428 and 9429 are identical
> except that the 9429 is jumpered for 80 tracks and the 9428 is
> jumpered for 40 tracks... but I'm not 100% sure.

They would have to have different heads, if the 40 track model was
standards-compliant and industry-compatible.  A head suitable for
80-track use doesn't write a wide enough track to reliably write to a
40-track disk that has been written with a normal head. It's likely
that the electronics is identical other than the jumper, and possibly
the values of some passives.

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