[Coco] Artifacting on LCD?

[LinuxRules]

Robert Gault wrote:
> Allen Huffman wrote:
>> Are artifact colors caused by the CRT or the composite/RF modulation?
>>
>> If I get an LCD TV or monitor with composite inputs, will it show 
>> artifact colors?
>>
>> Sent from my iPhone
>> Follow me on Twitter - http://twitter.com/allenhuffman
>>
>
> Artifacts are not cause by the CRT but rather the NTSC format. The 
> rapidly changing pixels appear to the composite demodulators as color 
> information as the rate of change has the same frequency as the color 
> burst. Difference in phase with the color burst gives the color.
>
> So if the LCD TV has a composite input which conforms to NTSC 
> standards, you ought to see artifact effects.
What he said!!! That's it exactly.

And as best I can remember with failing memory cells, the early 6847 
design would power up
in either of two states with the clock phase different. So the same data 
would produce a different
artifact color depending on how it powered up.

I don't recall if any of those ever went into production. (Several 
"patch" mask sets were made
early on, before and during early production.....) It was kind of 
strange to watch, though......

cheers,
john dumas
(Motorola circuit designer engr for 6847...retired)
JohnDumas at austin.rr.com