[Coco] Undocumented video modes

[L. Curtis Boyle]

On Mon, 05 Feb 2007 12:38:54 -0600, Leon Howell <puritan_2076 at yahoo.com>  
wrote:

>> There is also a wide 128 character text or 256 byte graphic screen using
>> bit7 at $FF9F (horizontal virtual enable). Coupled with vertical
>> scrolling can give you a graphics screen 256 bytes H by as large as your
>> memory permits V.
>
> Um...wow. 256 bytes wide means, at 2 bytes per pixel, 512X(192-225)-16.  
> I was
> sort of hoping for, but not taking seriously, the possibility of 16  
> colors
> above 320X225. Now it looks like that's possible.
>
> But wich is more amazing- 512X200-16, or 4-color mode, 1024X? It sounds  
> almost
> like you're even suggesting the possibility of 2-color, 2048X? How wide  
> can it
> really get?

     The horizontal virtual enable still only displays 320 (or 640) wide...  
it just allows you to make a larger screen that you can scroll through in  
hardware (256 bytes worth, which will vary in pixels depending on the # of  
bits per pixel you are using). Games like Crystal City use it.
-- 
L. Curtis Boyle