[sdiy] Floppy drive data [was: OTA book on eBay]

[Colin Hinz]

On Thu, 13 Oct 2005, Tom Arnold wrote:

> On Thu, Oct 13, 2005 at 11:20:47PM +0200, Rainer Buchty wrote:
>> For example, tried to get information on how floppy controllers work
>> lately? I mean, not just the basic blurb like "magnetic recording" with
>> nice pics of elementary magnets, but the hard tech facts (FM vs. MFM,
>> GCR, RLL codes). That stuff pretty much vanished from the web.
>
> Actually, I've been collecting that exact data extensively. :-)  I was
> fortunate to have the headstart of Sanyo MBC1000 service manuals from the
> late 1970's as a starting point.  I recommend datasheets from YE-Data ( teac
> and mitsumi data is worthless ) for floppydrive theory, and you can find
> info on controllers on most sites with info about BBC computers or upgrades
> for Sinclair computers.  Nice site in Finland has many popular floppy drive
> controllers.  Western Digital also provided me ( free of charge ) about 200
> pages of faxes for all their old controller chipsets.

Another coincidence: I recently found an old floppy (5-1/4", actually
floppy) disk in Acorn Atom format. Web browsing shows that emulators for
the Atom work with disk images only, and don't provide a means of
retrieving data from original disks. Looks like I need to build some
hardware using the ancient i8271 FDC chip I bought last year. Maybe
I'll give it a USB interface for fits and giggles. :-)

> In case anyone is curious why I'd be interested in this data, I've been
> working on a flash replacement for floppy drives that actually plugs in in
> place of the drive itself and deals in common disk images.  ie : for the
> mirage you use mread/mwrite images written to compact flash, for the DSS-1
> its CopyQM images.  That way I dont have to deal with writing the PC side of
> things, I just deal with the hardware and you use existing tools to make the
> images.  The timing is a PITA and has been my stumbling point.  I'm hoping
> in a few months to get back to work on this but I have other projects to
> finish right now...

Sounds like an ISA FDC card in reverse -- floppy interface on the host
side, with ISA (aka CF) interface for the peripheral. Too bad the WDC
chips don't have a 'backwards' setting. :-)

- Colin Hinz
  Toronto, Canada