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Re: C64/128 vs Apple -- Video?

Crosspost to comp.sys.cbm added back.

"Bryan Parkoff" <nospam@nospam.com> writes:

>>>Now, what about C64/128?  It has 40x25 lines so it looks like 640x200
>>>resolution.  Do C64/C128 use CGA font?  Is video circuit more complex, 
>>>but Apple II's video circuit is little simpler?  I am curious.

>>Commodore doesn't use artifact color. Their circuit creates the chroma
>>signal independently of the luma. So they are not bound to a 3.58 MHz
>>pixel clock. In Commodores, there are 7 (NTSC) or 9 (PAL) chroma cycles
>>per 8 luma cycles.

>Are you saying that C64 uses color reference in 7 MHz rather than 3.58 
>Mhz?  I know that all NTSC and TV are capable to use 3.58MHz for all TV 
>channels.  No matter how high frequency is, but it still uses artifact 
>colors.  How can color reference in 7 MHz be done?  What is the difference 
>between regular color and artifact color.  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?
>I hope that Michael Mahon will explain more how it is done to overcome 
>color artifact.

No, the VIC-II is still generating a chroma signal at 3.58MHz. Bob Yannes
talks about how the VIC-II selects and generates colour here:

	http://unusedino.de/ec64/technical/misc/vic656x/colors/

Scroll to the bottom.

--
      Cameron Kaiser * ckaiser@floodgap.com * posting with a Commodore 128
                personal page: http://www.armory.com/%7Espectre/
  ** Computer Workshops: games, productivity software and more for C64/128! **
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