17 Dec
2001
17 Dec
'01
11:44 p.m.
see below, plz.
Dick
----- Original Message -----
From: "Peter C. Wallace" <pcw(a)mesanet.com
To: <classiccmp(a)classiccmp.org
Sent: Monday, December 17, 2001 7:44 PM
Subject: Re: MITS 2SIO serial chip?
> The discussion of the SIO/DART arose from your apparent unawareness of the
> multi-channel serial devices that several manufacturers were pushing before
the
it
...and you have to generate an address strobe, and you have to deal with the
setup and hold time issues, which the bus doesn't. ... pretty much the same as
any other device costing a third as much. Of course it depends on whether
you're satisfied with "getting by" or would prefer to meet the spec's.
That would be a reason all right, though the 2681 had about as many, IIRC.
That's not what the extra parallel port bits
did, is it? I thought the
handshakes were still automatic. ... I've not had to hook up a serial device for
so long I can't remember the specifics. <sigh> Oh well... we always tie the
cable back to handshake with itself anyway, and rely on the X-on/X-off protocol
...
<snip
On Mon, 17 Dec 2001, Richard Erlacher wrote:
<snip > >
> > > The PAL16R/L/Xnnn series were quite a bit less costly, faster, and
more
> > > straightforward in their application than the Altera parts, however,
costing
> <$2
> > > in production lots.
> > > I think you are missing the point, In
1981 PALS were expensive...
> > Yes, they were, but the 8250 cost WAY more
back then than, say, a 2651 with
an
> external '393 counter. The makers of most of
the add-on I/O boards I've got
> lying about seem to have found PALs cost effective, BTW. That said, I
believe
> that I pointed out that the same task was readily
achievable with less than
> half-a-dollar's worth of TTL SSI logic. I think this discussion is
exhausted.
> PC was even a reality. The fact that you
don't like the interface
requirements
of the
DART/SIO for the ISA environment is clear,
I am perfectly aware of multiple channel serial chips, we used one in our
Sprite CPM machine in 1978...
And its not just that I dont like the DART in a ISA environment, I dont
think it even makes sense to use it as you suggested. I doubt that
there is a single add-on card that uses a DART for the ISA bus...
and, while I think it's at
> least as big a piece of rubbish as is the SIO, along with the other Z80
> peripherals, The 8250 isn't any better or worse for the ISA, IMHO, because
doesn't
take any more logic to interface the thing.
Takes much less logic, only a decode
Just because YOU don't like
<snip > I had to buy 8250's to populate multi-port
serial boards for various S-100
> systems back then and was acutely aware of the cost of an 8250 as opposed to
a
less
generously provisioned device. It had lots of parallel bits, that some
folks used, but I never needed them.
I pressume thats why IBM chose it since it supported a full set of Modem
control lines...