Date   : Tue, 10 Feb 2004 09:16:37 -0000
From   : "Richard Gellman" <splodge@...>
Subject: Re: Discs

Jules Richardson wrote:

> > Disc drives themselves come in different flavours too. PC 5.25" floppy
> > drives generally don't work with BBC discs, although they can be used,
they
> > have a different track stepping,
>
> For clarity, you presumably mean that standard PC disk formats use a
> different geometry (sector size, tracks, sectors per track etc.) when
> formatted on a PC using a *standard* format utility? The physical floppy
> *drive* hardware is the same, and assuming you get an necessary jumpers
> set up correctly, a drive sourced from a PC will work with a BBC.

Something more subtle than that. Typically the PC drives use a slightly
different drive stepping distance to the BBC ones. While track 0 will still
read fine, and possibily track 1, subsequent tracks tend to be misaligned.
Hence you can use either drive in either system, but any discs created in
"wrong" drives won't work in "right" drives.

Not all drives have jumpers, but you are right that some drives do allow you
to select the drive stepping on them. The 40/80 switchables based on the
Mitubishi board/mechanism (such as my Ahkter UFD400A drive) have about 20
(conservative guesstimate) jumpers that allow the drive to be used in many
systems. I've found that I can get success with the FDC program by setting a
jumper suspiciously marked "MS".

I think the bottom line on this one is not to expect "foreign" drives to
work, at least not without tweaking. If it does, then wallow in the glory of
your success.. if not, pick up a cheap BBC drive from eBay :)

-- Richard Gellman