game genie codes for booby kids

[darien dark]

these are all game genie codes I made for booby kids on the nes
infinite time (based on Rune's PAR code)
GNAGOI
infinite bombs
XAIVAL
invincibility (this one is better then VisitntX's version since it allows you to go into portals and trampolines)
EOPTGA

[Whipon]

^^

Nice job. But try to use the 8 letter format. 6 letter codes are a bit unstable, since the check value doesn't exists, so It patches every reference to the address given.
Also, If you want to patch the rom directly, the check value will help you greatly to find the correct rom address.
Just my two cents .

[darien dark]

thx for the feed back Whipon, sadly, I'm not too clear on how to make 8 letter formats, I know its got to do with the compare value, but I'm not too clear on how the compare value works or how to find it. plus my codes are rom addresses, I always though rom addresses where constant (unlike ram addresses) so they didn't need a compare value. anyways, I would like to know more about compare values, if you know of a good document I can read to find out more let me know.

[darien dark]

Sorry to double post, bu I'm kinda curious as to when (or if) these codes will be added to the database?

[Tony H]

Making an eight letter GG code is fairly easy if you know the actual ROM address of the code.

The compare value is simply the *original* value at the actual ROM address of the code. Example: Let's say at ROM address $1234 you have a value (opcode) of 85, and you want to change it to A5. Your compare value for that code would be 85.

It's been a long time, but if I remember correctly, the reason for the compare value is because the NES only loads 8k chunks of the ROM instead of the entire thing. This means there can be several different "8k" chunks in NES games. The compare value makes sure it has the right "8k" chunk. So if the NES loads an 8k chunk, it will check to see if the compare value matches the *original* value. If it doesn't match, it won't make any changes.

If you don't use a compare value (ie. a 6 letter GG code), every single "8k" chunk will be modified, even if it isn't the right one. As you can probably guess, this can cause problems.

[Whipon]

=)

Well, you know, nes uses mappers.

From Kodewerx Enhacklopedia:

The Game Genie, made by Galoob, is a cheat device, like the Pro Action Replay. However, unlike the Pro Action Replay, the Game Genie patches ROM, whereas the Pro Action Replay edits RAM. For example, a code may patch the address 0x8000 with the value 0x3F. This means that instead of modifying 0x8000 to be 0x3F, instead the Game Genie will watch for the game to access 0x8000, and whenever that happens it will send 0x3F to the location that requested 0x8000. This method, however, has one drawback. Because the 6502 only has a 16-bit program counter, only 64 KB of memory can be referenced at a time. To get around this limitation, the NES employs what is known as "bank switching". Basically, the NES references the entire ROM in 64 KB pages, and when necessary switches the page. What this means is that the assembly code referenced at our location 0x8000 is not always the same. It may refer to 0x8000 or 0x18000 or something else, but all will be patched. This can cause bugs, which is obviously undesirable. To combat this, Galoob provides an 8-character Game Genie code, which an extra byte called "compare". For this example, compare will be 0x5A. What the Game Genie will do is watch the address 0x8000 to be called. When it is called, if the value at that location is 0x5A, then 0x3F will be return. Otherwise, the Game Genie will allow the game to operate as intended. Game Genie codes also have to be encoded. Encoding and decoding Game Genie codes is explained in the sections below. It is worthwhile to learn how to do these operations by hand. However, while not very hard, it is quite tedious. GG Encoder automates this process for you. Finally, decoded Game Genie codes are expressed in the format aabb:cc for 6-character and aabb?dd:cc, where aabb is the address to patch, cc is the patch value, and dd is the compare byte.

So basically, lets imagine you want to modify this

$90F8 8D 03 03

In to

$90F8 AD 03 03

Your code will be:

90F8 8D AD = SXNOAESE

If you not include the replaced byte (the compare value) the code will patch every reference to 90F8.

[darien dark]

thx alot guys, I get it now, I'll fix them right away
inf time
GNEGOSSA
inf bombs
XASVAUSZ
invincibility
EOOTGAEY

[Tony H]

Oops, I incorrectly said the NES uses 8K chunks (pages). The "Enhacklopedia" shows it as 64 KB.

[darien dark]

its ok tony, I figured it out

[Hybrid]

got'em