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A 7800 hack request


Brian R.

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This got discussed in the 7800 forum, but it just sort of faded away. It's something I'd really like to know if is technically possible and, if it is, if there's someone out there with the skill and time to do it.

 

Do what? Hack 7800 Ms. Pac into Pac-Man.

 

We got Pac-Man Arcade on the 2600 - so despretely needed. But on the 7800 we don't even have Pac-Man.

 

I think a 7800 Pac-Man would be highly desired, enough to put it on a cart and sell it in the store. I know I'd buy it.

 

Can it be done? Will it be done?

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I am trying to figure out how to disassemble a 7800 cart - I used to know assembly back in my Apple IIc days, so I'm hoping I can remember it. Then, I plan on giving it a shot.

 

But if someone can get to it before me (it might be a while for me) that would be great as well.

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  • 3 weeks later...
  • 4 weeks later...

The Atari 7800 Software Guide is the place to start. Just be aware that each line of the sprites are stored on a separate page, with the bottom on the lowest page. Sprites will typically be stored on even 4K segments. Most 7800 games use 160A mode, with each byte being four four color pixels. Most of the other graphics modes are very strange and may be difficult to modify.

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Sure, it should be possible. And I'm sure there's people here who can pull it off. But just in general, there's no homebrews for the 7800. I think a few people worked on some for emulators, but that's not the same as haveing a real cart IMHO.

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Eric: Ya'know - I had a feeling I was up against something major when I couldn't even find where the graphics were held :( Your explanation makes me think that this is a little beyond me (at least at this point in my life - back when I was 16 I figured out how to program the Apple IIc in Assembly and knew what every memory location did; I *used* to be smart) :ponder:

 

This is probably why the Ms.Pac-Man -> Pac-Man conversion wasn't done already... :(

 

Maybe (if you're willing) sometime in the future we could work on it together? If you are familiar with where things are laid out in the cart, I will do whatever work it takes to get it there...

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Just for the heck of it, I put together the following tool. You feed it an a78 binary and it will create a PPM file. It assumes a 2 bit per pixel mode. Each page starts a new row, so each row is 1024 pixels wide.

 

I used IrfanView to vertically flip the PPM and turn it into the attached GIF.

 

Remember that the 7800 has 8 palettes.

 

Source is included.

post-2222-1056656388_thumb.png

a78sprite.zip

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Another good tool for sprite editing is YY-Char, if you can find it. You can select which Bytes Per Pixel setting you need, and you can edit the file directly. It might be good to use it for hacking some files, though it probably won't work correctly for 7800 games.

 

~Blackbird

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  • 7 months later...
Just for the heck of it, I put together the following tool.  You feed it an a78 binary and it will create a PPM file.  It assumes a 2 bit per pixel mode.  Each page starts a new row, so each row is 1024 pixels wide.

 

I used IrfanView to vertically flip the PPM and turn it into the attached GIF.  

 

Remember that the 7800 has 8 palettes.

 

Source is included.

 

how do i use this? i tried opening an a78 file with this and it just starts up and then closes immediately every time.

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  • 2 years later...

Wow, I didn't think a thread this old would still be on the first page of the forum! I was stunned to see it.

 

So, it was more than three years ago when I first asked the question - Can we have PacMan on the 7800? And more than three years ago since Bob said he was going to start tinkering with it.

 

And here we are, not with just PacMan for the 7800, but several versions of PacMan!

 

Well, as I long ago had predicted, all hail the hero! :D

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