[Coco] How to read CoCo floppies on a pc?

[Gene Heskett]

On Sunday 16 December 2018 12:23:09 farna wrote:

> The biggest issue is that since about when Windows XP debuted the
> floppy controllers stopped supporting anything under 720k drives. The
> OS doesn't support smaller drives either, but that can be rectified
> with software as already noted.  I suggest you either see if someone
> on the list will transfer the disks to a USB stick or card or get an
> older computer that is capable of operating a 5.25" drive. A 1.2mb
> drive will usually read a 360k, but DO NOT WRITE to it. That will
> destroy content and can render the disk unusable due to differing
> magnetic strengths an properties between the two drive types. Going
> from old memory, but something like that.... Sent from my Galaxy Tab A

The main problem Frank, is the width of the track on the 5.25" media, its 
only half as wide for 720/1.2meg formats, so the write, mechanical 
tolerance aside, erases only half the width of a 40 track. leaveing old 
data mixed with the new, and the drive gets hopelessly confused.  And 
the only recovery for that disk is to format it. Doing a backup from a 
good disk while its inserted in a 40 track drive might also work.

3.5" media OTOH is 135 tpi regardless, the data rate is whats changed, DD 
is slow, 250 kb for a 1.44 meg disk, HD is twice as fast, and QD is a 
megahertz but the higher capacity's need a harder magnetic coating to 
record that higher detail. So putting an HD or QD disk in a DD drive 
gets recorded so weakly by the DD drive that fading is a real quick 
problem. Taping over the HD holes puts newer drives in the weak, low 
current record mode, writing a very weak magnetic signal that fades 
rapidly. The coco's default data rate is only half that at 125 kb, and 
that makes the disk a 720k disk.

-- 
Cheers, Gene Heskett
--
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