[Coco] Undocumented video modes

[Leon Howell]

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?