exxos's Atari, Amiga & retro forum

Hi,

I suspect that many Atarians, especially older ones, have heard or read about the expansion of the AtariST computer's color display capability to 32k colors developed and described by Barry Orlando in the 32kcolors.zip file available on the Internet. Unfortunately - the file did not contain the schematic, but Barry wrote that for anyone who sends him a letter with feedback - he will send a copy of the schematic. Personally, I never lived to see a reply and I tried to contact him from 25 years ago.... Literally three days ago, our buddy Atarian - nicknamed ATREUS - from the Polish Atari Area, while browsing through old issues of Atari Interface magazine on the Atarimania site, made a remarkable discovery. Literally like Indiana Jones :). It turned out that in the October 1989 issue is published the text of the 32kcolor file, along with a complete diagram of this extension and a listing of a test program of its use. I am personally still in shock - how was it possible that for decades no one came across this document.... Eternal respect to Atreus for his curiosity and willingness to learn about the history related to various aspects of Atari computers.

Hat off.

Link to archive on Atarimania - https://www.atarimania.com/atari-magazi ... e_108.html - October 1989 page 24.

Regards
tOri

@tOriman That is amazing! A very long mystery possibly solved :D :thumbup:


I extracted the pages here :)

@tOriman Very cool, is this something you personally might design a PCB for?

Hi,

Not now because I can't. I think that Sporniket will do something more...I wrote only info here.

Regards
tOri

Very cool find. What chip is U27 and U23 that it is refering to in the schematics?

Isn't this the same thing? viewtopic.php?t=302

Hi,

I attach an explanation - it is most likely these chips from 520ST schematics (near SHIFTER)

tOri

Steve wrote: 15 Jul 2025 18:54 Isn't this the same thing? viewtopic.php?t=302

It is a nice try to recreate this project by @sporniket not exactly the same project.

tOri

@Steve Spornikets version is a (great) guess at the original design and enhances the palette by adding an extra bit so 16bpp/64k colours.

Great find :)

I will study that during the summer, to see if I need to amend something on my design. No promise though, because not enough time (and I never had a working ST to test it anyway).