[Coco] Undocumented video modes

[Leon Howell]

> 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?

I remember an article in rainbow that told how to use a 128-collum mode, but 
it only displayed 80 collums at once. How wide can it really get on the 
monitor?

How high can it get on the monitor, without scrolling?

Is there a way to change the Sync rate of the GIME?
 
> Misuse of the switches may result in unexpected combinations of the 
> above. That's not really undocumented as I think you mean it.

I first read about these strange modes on the "Gate Crasher" web site. You get 
to shoot Bill in what is called an "undocumented" 128X192-16 mode. That's the 
kind of stuff I was really expecting to find- more colors in the low-rez modes.

I also read what I think was a typo but might not have been that compared 
NitrOS-9 to another speed upgrade using a 640X129-16 window. Is it possible?
> 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.

I was just thinking of using pokes, etc, like on the C=64, to try them out. 
Maybe someday I'll actualy find an OS-9 Level II Development Pack with RMA.