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Old 05-18-2015, 09:52 PM
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wa2ise wa2ise is offline
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Join Date: Dec 2002
Location: USA
Posts: 3,124
I was part of a user group of the Atari 800 home computer at work 30 years ago. Our favorites were usually 2 player (at the same time) games.

Wizard of Wor

At work a few of us modified an Atari 800 computer so it could be synchronized to an external video source. Someone, who used to work for Atari earlier, said that Atari would have paid big money for that set up (to make it easier to make TV commercials of various video games (the game systems were only 240p, and the old analog broadcast TV system was 480i).

IIRC, we replaced the video timing oscillator (3.58 crystal) with the external synchronizer circuit. At every horizontal interval we paused the 3.58MHz signal fed to the computer for 140nsec (half a cycle of the chroma subcarrier). And as the Atari had "S-video" signals (luma and chroma) available at the 5 pin plug on the side of the machine, we could invert the chroma signal every other line (to compensate for the 140nsec delay), then add it to the luma signal. And during the vertical interval, we added sync timing signals to make the output video be interlaced.
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