[Coco] Artifact purple/green wasRe: CoCo Monitor

[Robert Gault]

Allen Huffman wrote:
> Some of the emulators have an artifact mode, but now I wonder:  How far 
> do they go?  Do they just simply do the "odd is red, even is blue" or 
> vise versa colors, or did they actually try to emulate all the 
> artifacting in NTSC?  That would let our PAL friends see them.
> 
>         Allen
> 
> 

MESS does an amazingly good job with artifact color. I just set up, side 
by side, MESS on my PC and a Coco3 with a composite monitor. The result 
was actually better with MESS.

The reason that the result with MESS was better is interesting. Tandy 
knew (eventually) that the strength of the artifact signal depended on 
leakage of the color carrier signal into the composite output. Some 
models incorporate an "antenna" wrapped around a lead from the MC1372 to 
increase leakage. The Coco3 circuit is very different because of the 
GIME and may not be as good with artifacts as a Coco 1 or 2.