17 Dec
2001
17 Dec
'01
11:53 p.m.
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(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, December 17, 2001 7:59 PM
Subject: Re: FDCs (was: MITS 2SIO serial chip?
NEC
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(a)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
> 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