[Coco] Undocumented video modes

[Robert Gault]

Leon Howell wrote:
> How many video modes does the CoCo 3 actualy have? I have read about 128X192-
> 16, 160X192-16, and 640X200-16, and 64-collum text (64X16,I think) which I 
> have actualy seen once when I bumped my MPI.
> 
> I know none of these are supported by D.E.C.B., and probably not grfdrv or gfx
> (2,3,5,etc) either. But there must be some way to use them from D.E.C.B. or 
> R.S.B. Commodore-64 style, using peeks & pokes.
> 
> What other modes are available, and how do I use them?
> 
> 
There are 13 documented Coco3 modes that do not include PMODE graphics:
text
32, 40, 80
graphics
640x4, 640x2, 512x4, 512x2, 320x16, 320x4, 256x16, 256x4, 256x2, 160x16.
All of the above graphic mode can have a V of 192, 200, or 215.

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.

Misuse of the switches may result in unexpected combinations of the 
above. That's not really undocumented as I think you mean it.

There really is no good way to use these mode from Basic. You have to 
write your own ml programs. The patching required to Basic would be 
extensive.