Re: Testing XY Output.

On Fri, 5 Oct 2001 mccullar@flash.net wrote:

> Unfortunately, Atari doesn't use that Z signal on all of their color vector
> games. I forget which one, but I recall trying to make use of it but found
> out that the mixing transistor had never been installed. Don't know why; it
> had been built that way from the factory.

I won't argue with your results testing a game, but what I was saying is
that there is no 'mixing transistor', nor any 'mixing' going on at all. (I
should say I am going by the Star Wars schematics here. )

There is one DAC that contols the intensity, and three latches that decide
what combination of colors is on at that intensity. In other words, you
can't have full-green and half-blue. The Z test-point is the raw output of
the (single) Z amplifer, regardless of color.

There is only one intensity driver, not three, so they don't get mixed.
It more like the Z is 'split' to the three colors.

This limits your color selections to basicly 7 colors (8 if you count
black), and I suppose contributes to the look of vector games as we know
them. I wonder how much more could actually be done if the three color
intensities could be individually controlled, and if it would have effected
the performancesof the CPU's of the time.

-Chris

==========================================================
Chris Candreva -- chris@westnet.com -- (914) 967-7816
WestNet Internet Services of Westchester
http://www.westnet.com/

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Received on Sat Oct 6 07:29:24 2001