[Coco] So, does anyone know where to get disk drives?

[Gene Heskett]

On Monday 02 September 2013 12:54:18 Steven Hirsch did opine:

> On Sun, 1 Sep 2013, Gene Heskett wrote:
> >> this drive will format in 360k when jumpered to 300k
> > 
> > As a blanket statement, that's Pure Fooey.
> > 
> > The magnetic drive to the head ONLY changes when a QD disk is inserted
> > in a QD drive.  The only physical difference is the width of the
> > track in a 96 tpi drive, is nominally 1/2 the width of the track that
> > the 48 tpi (180k SS, 360k DS) drive uses.
> 
> Gene, how does a 5.25" drive perform media detection?  I know that 3.5"
> HD media has an extra sensor knockout at the rear of the case, but I see
> no obvious physical difference between a DD and HD 5.25" diskette.
> 
> I've always thought that density select was strictly managed by pulling
> a line on the interface (i.e. the operating system's responsibility).
> 
> Steve

I don't believe there is one for the 5.25" diskette, the QD has another 
notch opposite the write protect notch.  AFAIK there is no diff in the 
magnetic characteristics between the 48tpi rated DD disk and the 96tpi 
rated disk other than a more critical surface scan, probably done on 1 per 
10,000 made basis.  But since I expect that the worlds supply of disks has 
been made & we are just cleaning out warehouse's in Sechwan, none of the 
currently available stuff has been subjected to even that close a look 
unless its been preformatted to messydos FAT12 stds.  Even that isn't fool 
proof, the verify read takes 3x the time that the format write takes, so 
failed format disks are likely not recycled because the time consuming read 
verify step was skipped.

Cheers, Gene
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