see below, plz.
Dick
----- Original Message -----
From: "Allison" <ajp166_at_bellatlantic.net>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, December 18, 2001 6:52 AM
Subject: Re: MITS 2SIO serial chip?
> From: Richard Erlacher <edick_at_idcomm.com>
>
<snip>
>
> Gaps are programmable too. There are two things the 765 will not do:
> Munged
> wacky formats like using deleted address mark for address mark {you can post
> format with deleted data} and it was not designed to pump out all the raw
> bits/splices/marks from the media.
>
What? I do seem to remember that the data fields could be written during
formatting with the WD parts but I don't think anybody ever used that feature,
though it would have been a good/smart feature for software duplication. There
was some confusion about whether it worked properly because the part responded
to some bytes by generating an address mark, though I doubt it did that while
writing the data field.
>
> Things it did do that the WD never had: Multiple seeks or recals, timing
> for the stepper, head load delay, head settle delay.
>
Did it do "implied seeks" wherein the controller looked at where it was and then
automatically computed the difference before moving the heads?
>
> The biggest difference: register based programming vs command packet to a
> "port".
>
Back in the '77-'82 period I was probably responsible for the use of 100K
Western chips and it might as well have been decided on a coin toss. I was
persuaded by the guys who sold 'em, and since Western was ultimately responsible
for the use of much of my time, I was happy to oblige. They always suited me
just fine. I'm not sure what you mean by this contrast between register based
vs packet programming though. Perhaps you could cite an example? The Western
part is certainly register based. Isn't the NEC part also just a register set?
>
> I've used both and someplaces one or the other is better. On the whole the
> WD
> parts always seemed to be first generation. The upside for the 765 based
> was the very highly integrated super chips like the 36c766 and later.
>
That was an advantage for those who were invested in a software base, but nobody
knew that back in '78-79. What's the 36C766? Google comes up empty. I've seen
some 37C665/666 types, but 36Cnnn? Who made them?
What's interesting, BTW, is that even Western, with its institutional prejudice
toward analog PLL's went with the 765 core once it went to the fully integrated
all-digital FDC, having dealt with the lower data rates in the 1770/72/73 chips,
which were not shown to be capable of 500 Kbps for some reason. Perhaps there
was some advantage in the 765 core that made it more amenable to integration
with a digital clock extraction circuit at the higher data rate. I doubt that
Intel would have gone for the 765 type if there weren't some manufacturing
advantage inherent in the silicon. That may be what's made the difference.
Intel certainly would have chosen the chip that was more economically
manufacturable, though maybe their primary economy came from the
already-established relationship (which they'd sabotage later) with NEC.
>
> Allison
>
>
>
>
Received on Tue Dec 18 2001 - 09:02:46 GMT