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SoundGammon

Using eproms question.

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I just broke open a Parker Brothers Popeye that I plan to put a hack of it into and I see it uses 2 2764 eproms with NO select chip, 7404. 

 

How is it that it doesn't need one but Atari cartridge eprom games do?

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Depends on how they map the game code. The cart slot has two 16K chip selects. If they map each 8K EPROM to a separate select line then they don't need an inverter chip.

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I disassembled Popeye and found the code is located in the $6000-$9FFF range. The 2 cart slot chip select lines map to $8000-$BFFF and $4000-$7FFF, so Popeye does cross the boundary and make use of both select lines. Some (most?) 16K games map to $8000-$BFFF, using only one select line, so they need an inverter chip when burned into 2764 EPROMs.

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We both noted that Popeye doesn't need the chip. Are you asking about another game?

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What I want to do is put hacks into extra carts, like these extra Pac-Mans I have.

 

Also, I want to do Realsports Football and change the names of "HOME" & "VISITOR" to actual team names!

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I disassembled Pac-Man and Football and found they are both located between $6000 and $9FFF just like Popeye. So your hack won't need any inverter chip.

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I should clarify: if you intend to put two 2764 EPROMs into the Pac-Man cart then you don't need another chip. You do need to rewire a few signals though.

 

If you want to put in a single 27128, then you will need another chip for the select logic.

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