[Coco] Sierra Xmas 86 demo

[Gene Heskett]

On Monday 10 December 2012 00:38:14 Theodore (Alex) Evans did opine:

> On 12-12-09 09:37 PM, Bill Pierce wrote:
> > Stephen...
> > Not sure about the 80 trk 5.25 but I think it's supposed to be dns=3
> > also. I think this applies to any double stepping drive and 80 trk
> > 5.25 fits the bill so let me rephrase that
> > 
> > SSDD - DSDD Single stepping drives should be dns=1 (35trk & 40 trk)
> > DSDD Double stepping drives should be dns=3 (80trk)
> > 
> > That should cover it better.
> > 
> > I think it has something to do with the timing in the step rate of the
> > double stepping drives. Gene could probably clarify this as he seems
> > to be "Drive man" and knows more about stepping motors than most.
> 
> The reason why is so that if you put 40trk media in a 80trk drive it
> will read it properly.  While this is largely immaterial on 3.5" drives
> (I actually do own a 40trk 3.5" drive so they do exist) going with dns=3
> on 3.5" drives allows the same image and descriptor for 3.5" and 5.25"
> 720k disks.

You could get away with that UNTIL you go to read somebody elses properly 
formatted 3.5" disk and can't.

Cheers, Gene
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