# Glitch City Laboratories Archives

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## Video Game Glitches Discussion

### Serious emulation problem with Monster Race (GB)? - Page 2

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#### Re: Serious emulation problem with Monster Race (GB)?

Posted by: Krys3000
Date: 2017-09-04 17:55:40
Hey, I have one of those GBA Movie Player! Good times playing NES on my DS Fat.

#### Re: Serious emulation problem with Monster Race (GB)?

Posted by: Stackout
Date: 2017-09-07 10:43:33
I finally took a look at the "bad dump", turns out it's not really a "bad dump", someone modified the ROM.
Entry point jumps to 0:00e0, which is just nops in the good dump, but this space was used to add the following code:
[tt]
ld a,0
ld [$6000],a
ld a,$30
ld [$6000],a
jp $0150
[/tt]
This code makes no sense, the header says it uses MBC1, where $6000 is a 1-bit wide register that flips between two different banking modes. Maybe this is for flashcart compatibility?
In addition, a [tt]ld a,1[/tt] got patched to [tt]ld a,0[/tt] at 00:024C, and again at 01:488E.
Finally, the header checksum got patched.

#### Re: Serious emulation problem with Monster Race (GB)?

Posted by: Parzival
Date: 2017-09-08 09:05:07
Well then… we have our answer.
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