[sebhc] hard sector substitute

Peter peter59 at sbcglobal.net
Mon Jun 28 19:50:14 CDT 2004

The standard single or double density drive rotates at a speed of 300rpm.
High density drives are faster at 360rpm. I don't know the relative
stability of the rotational speed, but would suspect that you may have more
trouble with a high density drive than a double density. This view is NOT
supported by any experience or testing - just a guess on my part ;)

peter59 at sbcglobal.net - http://www.geocities.com/anapro.geo/

> -----Original Message-----
>  Steve Thatcher and I talked about this a month ago. It
> seems like it would be a relatively easy project. One
> could do it with one of those PLL chips and a couple 555's
> from an analog side or just use a PIC to create the pulses.
>  It saves having to find hard sectored disks. It does require
> that the drive be in good shape. The rotational speed
> has to be nice and constant. I don't know what the
> tolerance would be but I suspect it is within the
> range that most drives would work fine.
>  As far as drives go, I'd suspect that a H17 would drive
> either a 720K or a 1.44M. Of course, it wouldn't be
> any faster. That would require a faster processor.
> You'd need to deal with any rotational rate change but
> I'm not sure what these are for these drives.
> As it is now, it is just about as fast as it needs to
> be between writing bytes.
>  I should note that my Z80 machine includes the jumper
> modifications to do double sided disk. If anyone wants
> this information, I can make some notes.
> Dwight

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