[Coco] Higher graphics mode (256 color mode?)

[Arthur Flexser]

A couple of questions occur to me:

1.  You say the graphics are repeated 4 times across the screen.  Could
there be any way in this mode to change one of the 4 areas without
similarly affecting the other three?  (I tend to doubt it.)

2.  Are we sure that this is really 1024 pixel resolution?  It could be,
for example, that the 4 areas are in fact only reproducing every 2nd or
every 4th horizontal pixel of the original screen.  Indeed, maybe the 4
areas are not entirely identical, but 1/4 resolution and each offset by 1
pixel horizontally from the adjacent area to yield the same number of
pixels as were there in the original screen.

3.  Why exactly might this have anything to do with a 256-color mode?

Art

On Wed, Jul 15, 2015 at 4:49 PM, Paul Wittkoski via Coco <
coco at maltedmedia.com> wrote:

> Hi everyone,
>
> At one time, I found a higher graphics mode that is not documented with the
> CoCo 3. It was 1024 pixels across and the pictures in pmode graphics could
> be seen 4 times across the screen. I am unable to pull the exact method
> from
> my computer since my 5.25" floppy drive blew a chip some time back. But,
> someone may be able to find it again from what I remember what I did. It
> may
> have been odd thinking at the time but I wondered if pmode and hscreen
> could
> be used at the same time. Following the machine code for pmode and hscreen
> in the unravelled series I found a specific poke to turn on pmode and
> another one for hscreen. When I used them together on a cm-8 monitor it
> produce a screen with 1024 pixel resolution across. I am not sure if this
> would also lead to the 256 color mode if someone messed around with it.
> Interesting enough, I have not ever heard anyone else describe what I have
> done. Maybe that's how Tandy hid the 256 color mode so well; right under
> our
> noses with pmode. I hope this information is useful to someone in some way
> after all of these years.
>
>