[Coco] Creating a Coco Floppy in DOS

[wdg3rd at comcast.net]

 -------------- Original message ----------------------
From: Chuck Youse <cyouse at serialtechnologies.com>
> I'm going to state something that might be obvious to some and not to
> others.  Be sure the 5.25" drive in your PC is a _double density_ drive
> -- most every drive you come across these days is the 1.2MB AT standard.
> They spin at a different rate and thus aren't very reliable readers and
> even less reliable writers of double-density media.

Extremely reliable readers, and very reliable writers _IF YOU BULK-ERASE THE DISK FIRST_.  High-density drives never have a problem reading lower-density media.  But writing to a disk that already has lower density data on it, the 80-track head records a narrower path than the 40-track head, leaving slop on the sides.  Trying to read that back on a 40-track head (same size that the 35-track original Coco disk drives used) causes confusion as the partial bits on the sides interfere with the intended bits in the middle.  This has been common knowledge since the Tandy 2000 showed up in 1983.  All Radio Shack Computer Center tech support geeks were told the week of the release  (mid-August as I recall, but my memory is far from perfect) and we told everybody who took one out the door not to mess up their IBM-style floppies.  (Yeah, I know, warning customers is an exercise in futility, especially if you really insist DON'T DO THIS).
--
Ward Griffiths    wdg3rd at comcast.net

"What I know [about the art of the sword] boils down to this:  If you see a guy running at you with a sword, put two rounds in his chest to slow him down, then one into his brain to finish him off".  Aaron Allston, _Sidhe Devil_