Re: Double hires mode color artifacts

[Dirk Thierbach <dthierbach@usenet.arcornews.de>]

pitz <wongpet1@msu.edu> wrote:
> Dirk Thierbach wrote:
>> vladitx <vladitx@nucleusys.com> wrote:
>>> On Sep 5, 9:41 am, Dirk Thierbach <dthierb...@usenet.arcornews.de>
>>> wrote:

> How do I test this on an RGB card?  I have a Taxan/Kaga RGB card 
> installed on my IIe, but no docs on its behavior.  Could I just run 
> Beagle Graphics and look at the results?

I haven't figured out yet what Beagle Graphics does, so unless someone
has and can enlighten us, I would just modify the framebuffer directly.
Though you could use Beagle Graphics to switch on dhires mode first,
and maybe init the screen. For this:


>>>> : I think I read somewhere that RGB cards for the IIe look at the high
>>>> : bit of each byte when displaying double Hi-Res.  The high bit tells
>>>> : the video hardware to display as B&W or as color.  You can set this
>>>> : bit differently for each group of 7 pixels on the screen.

something along

]&HGR
]&HCOLOR=2
]&HPLOT 0,0 TO 400,0

should give you a blue line at the top of the screen. Then drop into
the monitor and change the high bits:

]CALL -151
*2000.2004

2000- 22 08 22 08 22

*2000: A2
*2001: 88
*2002: A2
*2003: 88

This won't change them in aux mem, but if the RGB card uses the high
bit, *something* should happen (ideally, you'll see white dots instead
of a blue line).

Finally, for this:

>>>> says that you can set b&w mode for double-hires by disabling 80COL
>>>> when enabling AN3. Is that correct? Other postings in this thread
>>>> heavily dispute it.

try

*C00C:0

It will either put you in black&white double-hires mode, or you'll
end up in 40 column normal hires mode, with the output routines still
set up for 80 column, so do a reset afterwards.

If you can manage to hook up a normal NTSC TV to the Apple and do the
same, I'd be very grateful. (While you're at that, it would also be
nice to have confirmation that double-hires color 8 is reall brown
on a NTSC TV, and not some sort of olive-green. That's color 'J'
in the color palette image of the Beagle Graphics slide show).

- Dirk