Path: utzoo!utgpu!watserv1!watmath!att!att!rutgers!cs.utexas.edu!uunet!cbmvax!raible
From: raible@cbmvax.commodore.com (Bob Raible - LSI Design)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Maximum bitplane depth
Message-ID: <15588@cbmvax.commodore.com>
Date: 4 Nov 90 02:57:32 GMT
References: <1990Nov2.225553.8132@daffy.cs.wisc.edu> <8451@pasteur.Berkeley.EDU>
Reply-To: raible@cbmvax.commodore.com (Bob Raible - LSI Design)
Organization: Commodore, West Chester, PA
Lines: 12

FYI non-ECS and the newer ECS DENISE parts are implemented in older NMOS
technology. This limited the size of the color lookup table to 32
colors. EHB and HAM were obviously created in an attempt to maximize the
usefulness of the "extra" bitplane. The bandwidth indeed exists for 8
bitplanes, however adding the extra color entries to the CLUT would be
impractical due to size considerations as stated above. I played some
tricks on the original lookup table to get it to process 28MHz pixels in
ECS DENISE(8373 as opposed to 8362). I basically split the address and
data domains in half and let each half process alternate pixels. This
reduced the palette size to 4 out of a possible 64 colors(only 2 bits
each of red,green, and blue info). I hope this clarifies things a
little.