Re: IIgs emulator with 1024x768 resolution

["Redskull" <redskulldc@yahoo.com.au>]

"Steve Mentzer" <dropthistext.smentzer@pacbell.net> wrote in message
news:BpHj9.19$HF6.66957@news.uswest.net...
>
> I can be done. You are going to have some problems though.
>
> The quickdraw and several firmware routines hardcoded the resolution(s)
and
> the calc routines (in order to speed up execution).
>
> You will need to patch GS/OS and any firmware the directly assumes that
> 640x400 (or 320x200) is the fixed video resolution.
>
> There are many other issues as well. Maybe other folks can offer some
> additional input here.
>

Hi Steve (and Dosius),

Thanks for your thoughts.

I was toying with the idea of expanding the routines provided by
Quickdraw 2 with some extra 65816 based routines that could be
mapped into some currently unused space below the memory
occupied by the ROM3 256k rom. The routines could even be in
X86 native to speed things up a bit. (WinUAE does this when it
is mapping it's "RTG" (re-targetable gfx) to the PC screen)

Specifically, I had in mind to use the currently unused Bit 4 of
the Master Scan Control Byte set to 1 to signify that a 1024x768 screen
is required when calling the _QDStartup routine.
Bit 4 could be checked by any further routines, to determine whether the
existing routines are called, or new routines that are 1024x768 aware.

Any programs not specifically asking for a 1024x768 screen would get
the regular variety.
16bit programs that do everything "legally" through toolbox calls would
require minimal changes to operate on the larger screen.

The 1024x768 screen could have the same colours as a 320x200 screen,
and be mapped into Banks E2/E3 for example. Or if X86 routines are employed
it could be a straight DirextX based arrangement.