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Coleco Gemini TIA chip location?


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Was TIA a general purpose chip or a custom chip designed by Atari? I don't think Coleco could have used TIA without a license if it was an original Atari design. The reason why Coleco won the lawsuit filed by Atari was because the Gemini and expansion module were built entirely from off the shelf parts and didn't violate any Atari patents.

Edited by OldAtarian
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By the passive components nearby, I'm guessing it's the one on the left.

I agree, but won't be sure till I try I guess...

Is the pin-out of the Coleco TIA the same as the Atari TIA? If not, you'll just need to do some sleuthing to figure out which pins you'll need.

This is the problem, no one seems to know and its no where to be found on the net, surely i'm not the first to a/v mod a gemini!?!?

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Was TIA a general purpose chip or a custom chip designed by Atari? I don't think Coleco could have used TIA without a license if it was an original Atari design. The reason why Coleco won the lawsuit filed by Atari was because the Gemini and expansion module were built entirely from off the shelf parts and didn't violate any Atari patents.

This is exactly why everyone says the gemini can be modded just like a 2600, but can't confirm it.

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By the passive components nearby, I'm guessing it's the one on the left.

No guessing required. The two chips on the right bear type numbers SY6507 (CPU) and SY6532 (RIOT).

 

 

Is the pin-out of the Coleco TIA the same as the Atari TIA? If not, you'll just need to do some sleuthing to figure out which pins you'll need.

That is the crucial question, but not difficult to reverse-engineer.

 

 

Was TIA a general purpose chip or a custom chip designed by Atari? I don't think Coleco could have used TIA without a license if it was an original Atari design. The reason why Coleco won the lawsuit filed by Atari was because the Gemini and expansion module were built entirely from off the shelf parts and didn't violate any Atari patents.
This is exactly why everyone says the gemini can be modded just like a 2600, but can't confirm it.

The TIA was apparently either not patented, or manufactured under license by so many chip makers, that it did become a de facto "off-the-shelf" part. If I had a Gemini motherboard in my hands, plus access to VCS schematics that I already have on my computer, I could verify the Gemini "TIA" pinout in about an hour or less.

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It'd have to be the one near top left with "Coleco" printed on it.

 

On the other side you can plainly see the 2 chips are the 6532 RIOT and the 6507 CPU.

 

Finding if it's pin-compatible with a 'scope...

 

Get the pinout of the TIA, then use outputs from the corresponding pins:

. CSync - there should be a ~ 1 ms pulse at a frequency of just under 16 KHz

. Colour out - put a game in, preferably one that has a coloured background. You should get a high frequency wave output from this pin. You might want to use CSync as a trigger when monitoring this pin.

 

You could test other pins too such as the Luma ones. In all cases probably a good idea to have a game running as TIA would probably only output on CSync without one.

 

You also should be able to visually check (or just use the continuity test of a multimeter) stuff like the Data and Address buses, the R/W select, and the RDY line.

Also, the Luma pins should go through a resistor ladder, so their ultimate paths/destinations will be similar.

Edited by Rybags
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I have both and a scope, just not real proficient with one yet. What do I look for?

 

If your scope is analoguey, Set the scope to trigger off 60Hz line frequency, throw an Asteroids cart in both machines, and look at each pin in sequence. From experience working on my 4A50 cart, many of the pins have very distinctive patterns on an analogue scope while running Asteroids.

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