ALSPA Cpm box

Billy Pettit Billy.Pettit at
Mon Apr 23 15:52:03 CDT 2007

Jules Richardson wrote:
jim wrote:
[CA floppies]
> Any thoughts on the list as to how to archive the data?  I know
> that Lars H. is going to do his thing, and owns them, but more
> ideas would be welcome.

Lars said something to me at the weekend about the disks that he has being a

bit weird; the first track's laid down using FM density with the rest being 
MFM - and for some reason Imagedisk wasn't making sense of them even in
analysis" mode. I'm not sure though if that was *all* CA disks, or just some

of the ones he happened to have.


Billy responds:

I saw this a lot on the early 8" single sided drives.  The transition to
double density was FM to MFM.  The first track was preserved as FM so older
drives could still read the boot track and then check for double density

I thought it had died out when the first double sided units came along, but
obviously not.  Some of the early LSI could handle this so it was invisible
to the end user.

All of  our 8" test systems at Magnetic Peripherals used this format on the
double density disks.


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