Re: C64/128 vs Apple -- Video?

[Linards Ticmanis <ticmanis@gmx.de>]

Bryan Parkoff wrote:

>     Are you saying that C64 uses color reference in 7 MHz rather than 3.58 
> Mhz?

No. A NTSC Commodore uses a 14.31818... MHz crystal. From this it
derives a color clock of 3.58 MHz and an independent ca. 8MHz pixel clock.

> How can color reference in 7 MHz be done?

It can't. Color reference is always 3.58MHz in NTSC.

>  What is the difference 
> between regular color and artifact color.

Artifact color: you create a single square wave type signal. The TV
"sees" a chroma and a luma signal in it that you never created as such.

Regular color: You create two different channels for luma and chroma.
Then you either mix them for Composite video or you don't for S-Video.
Anyway, the TV will recreate approximately your two input channels.

>  For example, Apple II uses Deep 
> Red which it is two pixels out of four pixels plus black gap.  Do color 
> reference in 7 MHz fill Deep Red in four pixels?

There is no 7MHz color reference. The Commodore creates deep red by
setting the luma channel to "fairly dark" and the chroma channel to "red".

>     I hope that Michael Mahon will explain more how it is done to overcome 
> color artifact.

-- 
Linards Ticmanis