Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!ucbvax!pasteur!cory.Berkeley.EDU!navas
From: navas@cory.Berkeley.EDU (David C. Navas)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Maximum bitplane depth
Message-ID: <8451@pasteur.Berkeley.EDU>
Date: 3 Nov 90 19:59:49 GMT
References: <1990Nov2.225553.8132@daffy.cs.wisc.edu>
Sender: news@pasteur.Berkeley.EDU
Reply-To: navas@cory.Berkeley.EDU
Lines: 26


In article pochron@cat44.cs.wisc.edu (David Pochron) writes:
>The question is this:
>
>    The Amiga can output 4 bitplanes of data in hi-res mode, (pixels output
>at twice the rate of lo-res...)
>
>So what were the bandwidth limitations that prevented the current set of
>chips to output 8 bitplanes in low res?  Is there some sort of "hidden
>overhead" inside the chip design that does not affect external devices such
>as HAM-E?

Well, yes.  Firstly, Denise lacks 224 of 256 color registers necessary to do
the job.  Also realize that she is responsible for taking bitplane information
and "de-planing" it.  There is significant overhead for the CLUT-type stuff
(Color LookUp Table), which is why super-hires had to restrict it's palette to
only 64 colors.  I'm not sure what impact that would have in lo-res, but I
wouldn't be suprised if it was significant...


Now I'm no techie with inside knowledge about how Denise works, but those are
the things I can think up off-hand.

David Navas                                   navas@cory.berkeley.edu
"Excuse my ignorance, but I've been run over by my train of thought."  -me
								(and Calvin)