Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!sun-barr!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Graphics Chips
Message-ID: <21173@cbmvax.commodore.com>
Date: 2 May 91 21:00:23 GMT
References: <1991May2.030706.30302@kuhub.cc.ukans.edu>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 33

In article <1991May2.030706.30302@kuhub.cc.ukans.edu> 2fmlhiccup@kuhub.cc.ukans.edu writes:
>Here is a quick question...

>   Why is it so difficult to make display chips for the Amiga that will 
>allow it to do resolutions/colors that i see on VGA?  What are the hardware
>and software limitations?

VGA chips are very simple chips.  They were originally simple enough for IBM
to build as a gate array (VGA == Video Gate Array).  Amiga chips, on the 
other hand, are considerably more flexible, but also much more complex,
and could only be built as full custom devices.  I would guess that an 
implementation of the Amiga chips that does, more or less, the same resolutions
as the basic VGA, 640x480x8 with 24 bit CLUT, would wind up more complex than
IBM's latest XGA chips.  You're certainly getting something for all that extra
complexity, but it's not as easy to crank out.  And of course, those several
hundred Amiga chip registers should stay as compatible as possible in any 
such new design, or all those idiots bypassing the software interfaces will see
their software break.

To give you an idea of the relative timing of gate arrays vs. full custom, 
consider the A3000.  I got seven revisions of the Buster chip between December
'89 and May '90 (the last few revs were relatively minor compatibility tweaks).
The last time I was waiting on a full custom part, the Chip Guys gave me two
revisions in about the same time frame.  The difference between 5,000-10,000
transistors and 100,000 transistors can be a significant one.

>Jason Wilson


-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
      "That's me in the corner, that's me in the spotlight" -R.E.M.