Re: TECH: AppleColor RGB Sync frequencies and dots sent Question

[Rubywand <rubywand@swbell.net>]

Eric Jacobs writes ...

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> > In article rubywand@swbell.net writes...
> > >
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> > >  Including the left and right borders, how many dots are actually > > >  sent per line in 320 and 640 modes?

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> 
> Including the left
> and right borders, plus the horizontal retrace, the video sends out
> more than 320 or 640 "dots" before the screen begins scanning the next
> line.

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> 15.699 KHz (3.579545/.228). This is well within the tolerance of most
> monitors. So therefore in 320-mode 228*2 = 456 "dots". In 640-mode
> there are 912 "dots". I put dots in quotes because, obviously, only
> 320 or 640 of them are actually seen as part of the screen.
> 
> When the GS is outputting a composite video signal, each horizontal line
> must contain a horizontal sync pulse and color burst, and there can't be
> a border during this time, or else the TV won't register a sync. On the
> RGB, the GS puts the border color on. So, the answer to your question
> is 456-320 or 136 pixels in 320-mode and 912-640 or 272 pixels in 640-
> mode.

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     Thanks for the information and backup details!



Rubywand