FDCs (was: MITS 2SIO serial chip?

From: Richard Erlacher <edick_at_idcomm.com>
Date: Mon Dec 17 23:53:14 2001

There had to be some advantage, though I probably never capitalized on it
myself, but I always got along with the WD chips just fine, hence never designed
in a NEC part even once. The earlier Western parts had some really long data
hold time requirements that were somewhat painful, but once I understood how to
make 'em work ... the rest was duck soup. Western had 'em working when I got
there and I didn't break 'em.

Dick

----- Original Message -----
From: "Fred Cisin (XenoSoft)" <cisin_at_xenosoft.com>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, December 17, 2001 7:59 PM
Subject: Re: FDCs (was: MITS 2SIO serial chip?


> There ARE many things that the WD will do that the NEC won't, including
> writing much sooner after the index pulse, IGNORING certain fields in the
> sector headers when reading, and a track read and write (the NEC has a
> multi-sector read and write instead of a track R/W)
>
> Allison could probably gives us a more comprehensive and authoritative
> list.
>
>
> On Mon, 17 Dec 2001, Richard Erlacher wrote:
> > Gee! ... and I let those guys at Western convince me you couldn't do that.
> > I've never attempted anyting with Int13, BTW, since I don't hack the PC's.
I'm
> > afraid to break something. I've got a '765-based machine I can experiment
with,
> > though.
> > Dick
> >
> > ----- Original Message -----
> > From: "Fred Cisin (XenoSoft)" <cisin_at_xenosoft.com>
> > > Yes, you can. Correction. I, and others, can. I shouldn't claim that
> > > you can.
> > > But Int13 won't. That is NOT the same as the chip not being able.
> > > You need to assemble an array of the sector headers that you want.
>
> > > On Mon, 17 Dec 2001, Richard Erlacher wrote:
> > > > There's one advantage that you can exploit with the WD parts that the
NEC
> > parts
> > > > won't support, and that's formatting with interleaving. The NEC parts
seem
> > to
> > > > be unable to format a diskette with other than strict ordinal sector
> > numbering,
> > > > while the WD allows you to number them with any offset you like. The
result
> > is
> > > > that an interleaved format optimized for one set of system parameters
can
> > still
> > > > be read by another system without the other system having to be adjusted
in
> > any
> > > > way. Of course it won't be able to read an entire track in one
revolution,
> > but
> > > > it will have the ability to read the diskette without introducing a
modified
> > > > lookup table for sector numbers. I know that doesn't make much
difference
> > > > nowadays, but back when folks used floppies as their main/only storage
> > medium,
> > > > it impacted performance.
> > > > Dick
>
>
Received on Mon Dec 17 2001 - 23:53:14 GMT

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