[Coco] RGB to XGA (Bruce Borer)

[Bruce Borer]

Hi Andrew,
    I got 225 lines working on my converter.
I now supports 32, 40 and 80 characters per line,
192, 200 and 225 lines and
256 colours (3,3,2).
   The new version of firmware needs to be uploaded to GitHub,
probably this week.  I also want to demonstrate on UTUBE.

Bruce P. Borer

On Wed, Dec 24, 2025 at 12:37 AM Andrew Ayers <keeper63 at cox.net> wrote:

> Hello Bruce,
>
> I was trying to point out that there are other GIME graphics modes which
> it can display (and they can be used, but there isn't many applications
> that do - I think the majority of apps that do are recently written
> (post-1992ish?) games); also, the 225-line mode (and the others that
> exist, I forget their values).
>
> I was just asking if you had tested all of those with your converter,
> since you mentioned only the 192-line mode, for instance? The tweaks to
> get the higher number of lines were something that was well known "back
> in the day", so there might (or is?) more software that uses them
> (versus the alternate GIME graphics modes, which while likely known,
> were either little exploited, or not at all).
>
> And the "256-color" artifacting mode is just something from the
> composite output that - while "sorta-kinda" was known about by some back
> then, it wasn't widely published about; I know of one publication about
> it in Hot Coco - but I've not found anything about it in the Rainbow;
> someone who worked for - I think Sundog? - supposedly knew about it, but
> for some reason, it was never known or experimented with, that I know
> of, by other users or developers (a curious tale which we'll likely
> never know the reasons why - I surmise that people were so enamored by
> the more colorful modes, and RGB output, that for some reason it never
> occurred to them to play around with the 640x192x4 color mode with the 4
> grayscales and do the same "magic" as the PMODE4 screen).
>
> The CoCo 3 has limited SG modes; SG4 and I think SG12/24 (???) - I'm not
> sure; the former is of course fully supported, while the latter two (or
> one?), like the CoCo 2, requires some special "POKES" and such to
> access, and for speed you need to use ML. Also, unlike the CoCo 2 VDG
> modes, it can't mix text with the semigraphics.
>
> Because you say your adapter works in WIDTH32, those modes should be ok,
> I would think - but testing them could reveal differently.
>
> Of the links I posted to you, the 3D printed "enclosure" should be of
> interest, since it was designed for a video mod primarily, but also that
> it fits inside the recess you spoke of; in theory it could make your
> adapter a more "commercial" kind of device - but since there aren't any
> design files, you'd either have to somehow convert it back into those
> (not sure if there are any tools to go from an STL to some other 3D
> editor or CAD formats) - or re-engineer it entirely.
>
> Ultimately, I was just wondering if you had tested all the known
> graphics modes the CoCo 3 can work in, or just a limited subset, and if
> the latter...perhaps trying those other modes and/or adapting your
> hardware and/or code to support them might be of interest to you.
>
> Andrew L. Ayers
> Glendale, Arizona
> phoenixgarage.org
> github.com/andrew-ayers
>
> On 12/23/25 9:26 PM, Bruce Borer wrote:
> > Hi Andrew,
> >     You seem to be asking about changes to the CoCo itself.  My
> > converter just displays what the CoCo3 produces, including making WIDTH
> > 80 readable on readily available monitors.
> >
> > Bruce
>