[Coco] Re: Any documentation or info on Tandy's Coco hard disk controller?

[Ward Griffiths]

On Wednesday 10 March 2004 09:41 pm, John E. Malmberg wrote:
> John Guin wrote:
> >  Hello all,
> >
> > I managed to snag one of these hard disk controllers at a garage
> > sale, and it powers up to "Disk Extended Basic 1.1" on my Coco2.
>
> I was under the impression that there were no ROMs in the unit from
> previous discussions on this forum.
>
> > But that's all I can do with it - I have no documentation for it
> > otherwise. Does anyone know anything about it or where to point me
> > for docs?  I looked through Marty Goodman's hard disk article from
> > the Rainbow (July 89?), but it did not mention the Tandy
> > controller.
>
> As I understand it, the controller was just a bus adapter that
> adapted the COCO bus to match the hard disk espansion interface on
> the TRS-80 models III/IV.

That is exactly the situation.  The adapter will only work with a Tandy 
primary hard disk unit (that can slave up to three secondaries).  The 
interface cards for the 2/12/16/6000 business systems were also bus 
adapters to match the 3/4 expansion bus.  (Except for the first Mod 2 
HD subsystem -- the physically bigger 8.4Mb drives were very different.

> The actual hard disk controller is an MFM controller in the hard
> drive 0.  An MFM disk controller can typically controll up to four
> 150 Mb drives if you can find them that work. :-)

The Tandy system was good for 8 heads by 1024 cylinders, or about 70 Mb 
per drive max.  There might be a way to increase that by changing the 
HD controller chip, but any WD2010 chips _I_ find will be reserved for 
my AT&T Unix PCs.  (The 7300 and 3B1, built by Convergent Technologies 
around an MC68010, not those Olivetti/Intel things).

> At the last time I priced used MFM drives from a dealer of that size,
> it was far cheaper to buy a Cloud Nine or Glenside IDE controller and
> a compact Flash unit.

There is that.  I need to study those schematics to see if they can be 
adapted to the 7300/3B1 or even the Tandy 6000.  My stash of mfm ST-506 
interface drives is gradually dying.  Got a handful of ESDI drives with 
nothing to put them in, if anybody's interested.  La Esposa is always 
at me to clear stuff out of the basement, and I don't have an emotional 
attachment to the ESDI drives.
-- 
Ward Griffiths    wdg3rd at comcast.net    http://home.comcast.net/~wdg3rd/

"And I don't like the idea of going _anywhere_ near the gods.  We're
like toys to them, you know."  _And they don't realise how easily the
arms and legs come off_, he added to himself.
                                Terry Pratchet, _The Last Hero_