Path: utzoo!attcan!uunet!lll-winken!lll-lcc!pyramid!octopus!pete
From: pete@octopus.UUCP (Pete Holzmann)
Newsgroups: comp.sys.ibm.pc
Subject: Re: GATHER and say NO to MCA!
Summary: AT bus is sufficient for the *near term*, from a *user's* pt of view
Message-ID: <267@octopus.UUCP>
Date: 30 Jun 88 17:44:18 GMT
References: <42900016@uicsrd.csrd.uiuc.edu> <257@octopus.UUCP> <978@gethen.UUCP>
Reply-To: pete@octopus.UUCP (Pete Holzmann)
Organization: Octopus Enterprises, Cupertino CA
Lines: 61

In article <978@gethen.UUCP> farren@gethen.UUCP (Michael J. Farren) writes:
>[Before I start, one question:  Mr. Holzmann, have you ever designed a
> high-speed digital bus?  I have.  Now, on with the show...]

Not personally designed. Worked at the gut level on, yes. Been around for
FCC hassles, yes. Is a 295 Mbit digital telecommunications architecture
fast enough for you?

>>My conclusion: the clone-makers need to pick a 32-bit AT bus exBension
>>	standard. There is little engineering reason (right now) to go to the
				  ^^^^^^^^^^^ a VERY bad choice of word
				  there on my part. Sorry!
>>	MCA.
>
>Unless you count greater reliability, better support for advanced architecture,
>better support for I/O, greater noise resistance, less emissions problems
>(therefore easier to get FCC type approval, therefore cheaper), etc....
>
>Not that I think that MCA is the BEST bus around, mind, but anyone who
>claims that the AT bus is sufficient is talking through his engineering
>hat.

Actually, I was talking from under my user's hat. I guess I shouldn't let
myself go like that! :-) I shouldn't have said 'little engineering reason
to go to MCA' without saying: Users want a compatible bus so they can
keep their investment in boards. I guess my attitude is that the AT bus
is going to survive a long time, simply because there is so much stuff out
there that uses it. I agree, the AT bus is an engineering disaster. But
users don't see that, and it looks like there's enough engineering miracles
left to keep users happy as long as they don't need 32 bit data paths.

On the other hand, I *do* agree that a new bus standard is needed. I really
like what the clone-makers are doing. It looks like there is an active push
going for the NuBus. Wouldn't it be amazing if Mac and PC boards eventually
became compatible with each other!?! That'll be the day.

>>1) MCA is cleaner, newer, nicer, etc etc:
>>	All true, all irrelevant. On a bus, what works is what counts!
>
>This is true.  However, what is NOT true is the claim that the AT bus
>"works".  No 32-bit data/address path, insufficient DMA and interrupt
>support, insufficient attention to loading and timing details essential
>to truly high-speed operation, and a god-awful electrical emissions
>characteristic.  I es?n't blame IBM one bit for getting rid of the damned
>thing.

From an engineering point of view, you are absolutely right. But from a
user's point of view, the AT bus is *great*. Just about everything is
compatible. And there are new boards that get around the DMA problems.

As an engineer, I appreciate with some amazement the amount of sweat that
must have gone into making this stuff work on the AT bus. I'm also amazed at 
how well the users are insulated from gory details of timing, low level 
formats, and other stuff. Imagine an end user even adding their own printer 
port to a computer 10 years ago! It wasn't fun.

Pete
-- 
  OOO   __| ___      Peter Holzmann, Octopus Enterprises
 OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014
  OOOOO \___/        UUCP: {hpda,pyramid}!octopus!pete
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