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BUG on GAMES5 cart for MunchMan


Shift838
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I think I found a bug on GAMECART5 for MunchMan.

 

while attempting to conquer the high score. I noticed that I could not get past level 1!

 

The entire screen has the chainlink laid down but it never goes to the next level. I tested it on actual hardware and classic 99 with the same results.

 

See screenshot. I don't see anywhere a link is not completed.

 

Anyone else have this issue ?

 

 

post-35187-0-51623900-1439512127_thumb.jpg

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This is (likely) the bug we found when doing the scratchpad loader. Munchman has a bug where it counts down the number of dots left (or links left) as a byte, but compares to zero as a word. If the other byte in scratchpad was not zero when Munchman started, you can never finish the level.

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This is (likely) the bug we found when doing the scratchpad loader. Munchman has a bug where it counts down the number of dots left (or links left) as a byte, but compares to zero as a word. If the other byte in scratchpad was not zero when Munchman started, you can never finish the level.

 

Is there a fix for it?

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Is there a fix for it?

 

Just making sure your loader zeros scratchpad... we didn't code a fix for it since everyone already has a binary.

 

I went and hunted down the message where we described the bug over on the SWPB group on Yahoo: https://groups.yahoo.com/neo/groups/SWPB/conversations/topics/2280

 

Here's the skinny:

 

 

 

I had ONE problem left which I have finally identified -- it is a bug in

Munchman. Munchman uses the byte at >8335 to count how many links you

have laid down. It uses a MOVB to initialize it. However, it uses INC

@>8334 to increment it, which would probably be okay, but it ALSO uses

C, rather than CB, to test it. Meaning if >8334, which Munchman /never/

initializes, is not >00, you can never clear the level. And that is what

is happening.

 

So, to fix, we just need to make sure >8334 is cleared before Munchman starts. It can go anywhere since it only needs to be done once. I dunno how many versions of Munchman are floating around out there, though.. I can patch the copy I have but will it do any good for anyone?

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It was tough to find a good place to put the clear... both the menu and Munchman are tightly packed and all the copy code is hard coded. I ultimately opted to put it in the copy loop itself, changing the bank switch code out to make room. This appears to work. It should not affect anything but Munchman.

 

Because I shifted code around, it's more than a couple of bytes, but there's a text file included that shows what I changed.

 

Gamecart5_TursiMunchmanHack.zip

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It was tough to find a good place to put the clear... both the menu and Munchman are tightly packed and all the copy code is hard coded. I ultimately opted to put it in the copy loop itself, changing the bank switch code out to make room. This appears to work. It should not affect anything but Munchman.

 

Because I shifted code around, it's more than a couple of bytes, but there's a text file included that shows what I changed.

 

attachicon.gifGamecart5_TursiMunchmanHack.zip

 

Thanks Tursi! Works like a charm..

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It was tough to find a good place to put the clear... both the menu and Munchman are tightly packed and all the copy code is hard coded. I ultimately opted to put it in the copy loop itself, changing the bank switch code out to make room. This appears to work. It should not affect anything but Munchman.

 

Because I shifted code around, it's more than a couple of bytes, but there's a text file included that shows what I changed.

 

attachicon.gifGamecart5_TursiMunchmanHack.zip

 

Blasting-you-rock-image.jpg

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  • 2 weeks later...

Just now seeing this, wish someone would have sent me a PM. Thanks for the patch, Tursi. Always nice to see an alternate way of doing things.

 

I've integrated the fix into the 1 meg gamecart as well.

 

Gazoo

 

attachicon.gif1megGames08312015.bin

 

 

 

Sorry Gazoo. I should have sent you over a PM. I dropped the ball on that one.

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