Path: utzoo!attcan!uunet!portal!cup.portal.com!doug-merritt
From: doug-merritt@cup.portal.com
Newsgroups: comp.sys.amiga
Subject: Re: Suggestion for New Graphics Chips
Message-ID: <7107@cup.portal.com>
Date: 4 Jul 88 16:18:37 GMT
References: <11415@steinmetz.ge.com> <4172@cbmvax.UUCP>
Organization: The Portal System (TM)
Lines: 39
XPortal-User-Id: 1.1001.4407

Dave Haynie writes:
>The current Amiga chips were done in old NMOS. [...] you can't just take a
>complex NMOS design, at any level, and crank out the same thing in 1.25
>micron CMOS [...] a full custom design is a mass of transistors and a
>by-hand layout (unless you've got a silicon compiler). Most layouts
>aren't scalable                     ^^^^^^^^^^^^^^^^
        ^^^^^^^^

This is comparable to the question of whether to write software in
assembler or in C. It's taken quite some years, but by now most companies
realize that by default, C should be first choice, with assembler used
only when absolutely necessary.

Similarly there has been quite a lot of resistence to using anything but
by-hand random logic for silicon. There are many people who sneer at the
mere notion of using even so much as (scalable!) Mead-Conway design rules.
For some cases, this makes sense, just as assembler sometimes does...
sometimes you need to squeeze as many gates as possible onto as little
real estate as possible, etc.

But not as often as some people think. In this day and age, it makes all
kinds of sense to use a silicon compiler as first preference. And they
*are* widely available. They can save vast amounts of development time.
The resulting silicon tends to have many fewer errors, reducing the
number of custom foundry runs needed to get a viable chip, and reducing
the support costs otherwise incurred by chips in the field with subtle
problems.

And you can always hand-optimize the layout after you've got working
silicon if you want to reduce the size or increase the speed or some such.

I'm sure Dave knows all this; I just cringe when I hear things like
"*if* you've got a silicon compiler". Everyone should have one!
(Everyone? Well, hobbyists need a Heathkit ASIC Foundry, too, I suppose :-)
	Doug
--
      Doug Merritt        ucbvax!sun.com!cup.portal.com!doug-merritt
                      or  ucbvax!eris!doug (doug@eris.berkeley.edu)
                      or  ucbvax!unisoft!certes!doug