[Coco] CoCoMax (was) Re: Introducing myself - Carlos Bragatto - Now: OT Amiga / CoCo musings

Andrew keeper63 at cox.net
Sat Apr 7 11:48:30 EDT 2007

I have both an Amiga 2000 and a 1200 - and I didn't know there was a 
connection between them and my CoCo. It seems the connection is a little 
tenuous, but it is there, nonetheless.

For the following, realize that I am talking out my rear, but I am 
pretty sure I am close with the information - correct me where I am 
wrong, and don't flame me too hard.

I don't think the CoCo Max 3 palette swap trick and the Amiga HAM mode 
have anything to do with each other, personally. For one, the HAM mode 
was merely using the hardware (mainly the Copper, IIRC) to do something 
it was designed for (but not documented well?), but in a unique way. 
When an image was displayed in 4096-color HAM mode - it was a solid 
image - no artifacts, no noise, nothing. Your only limitation was that 
you couldn't do any animation (and I would be willing to bet, though I 
never saw an example, that this limit could be overcome by someone 
willing to do it - maybe a democoder). The "super HAM" mode on the 1200 
and 4000 worked in the same way.

The palette swap trick on the CoCo 3, though, used a technique with the 
hardware to do something it wasn't really designed for, let alone 
documented. Somebody saw something in the hardware, a bulb lit up, and 
they tried it - lo and behold it worked. But it had noise (that junk on 
the left edge) - the video hardware wasn't designed to do this, unlike 
the custom chips in the Amiga.

As far as whether it had been done earlier? Not sure here - when was 
CoCo Max 3 first advertised? I have in my hands here the January 1987 
issue of the Rainbow. On page 20 (continued on page 24) is an article by 
Rick Adams and Dale Lear (are they on the list?) entitled "Color Chart 
for the CoCo 3" - which is also a 64 color chart. Interestingly, on 
pages 22-23 (in the "middle" if you will of the article) is a Colorware 
CoCo Max II advertisement - with no mention of CoCo Max 3. So - did 
these guys do this trick before CoCo Max 3 - and it was incorporated 
into it. Or, did development (and idea) paths cross (ie, CoCo Max 3 was 
in development at the time the article was released, but because it was 
a proprietary product, Colorware wasn't going to release that special 
code, and so someone else beat them to it)? I don't know. Does anyone?

Finally, at the end of the article, the authors write: "You may have 
noticed this effect on some video games on the Atari VCS, which uses 
this same technique to expand the number of available colors."

The "effect" they speak of is the "noise" on the left hand edge of the 
screen. They are right - this was done on the Atari 2600/VCS, for 
certain games. The only one I can think of off-hand that did this was 
the Battlezone cartridge (which, IIRC, was released when the tiny 
updated Atari 2600 system was released in the 1980s? - BTW, the 
cartridge works great in my vintage 2600) - but there are probably a few 
other examples.

So, obviously, this kind of a trick is pretty well known, and if you 
have few enough colors and enough processing power, you can even get 
motion on the screen. Hmm - makes me wonder if that is how Sock got some 
of his amazing demos to run? I have always thought that there should be 
a way to use the "64-color mode" (or some variant of it, maybe with less 
colors) in a graphic demo or game, or something. Sock, can you shed any 
light on this? I know your hi-color programs use a variant on the trick 
(it, combined with some form of pixel offset/rotation trick like NTSC 
uses to cut flicker and increase colors displayed)...

-- Andrew L. Ayers
    Glendale, Arizona


Message: 8
Date: Fri, 06 Apr 2007 17:23:58 -0500
From: Joel Ewy <jcewy at swbell.net>
Subject: [Coco] CoCoMax (was) Re: Introducing myself - Carlos Bragatto - 
Now: OT Amiga / CoCo musings
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
Message-ID: <4616C87E.1020407 at swbell.net>
Content-Type: text/plain; charset=ISO-8859-1

Gene Heskett wrote:

 >> On Friday 06 April 2007, Joel Ewy wrote:
 >> ...
 >>>> Don't forget that the Tim Jennison of NewTek fame is the original 
 >>>> of CoCoMax.  That, if nothing else, is some direct cross-pollination.
 >> I hadn't been aware of that!  Talk about cross-pollination, that's hand
 >> carrying the flowers to each other with introductions.  To heck with 
 >> bees.  Now I have to give credit for the history lesson, thanks Joel.
 >> Now I'm sorry I never bought a cocomax kit.

I'm not sure what the time relationship was between CoCoMax III's
palette-swapping routine and NewTek's Dynamic HAM. (Of course, by this
time Jennison was doing Amiga stuff, so any connection would be
indirect.)  Probably the idea of re-loading the palette registers
multiple times per screen isn't original with either the CoCo or the
Amiga.  Anyone have any idea where it was done first?

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