Convert a 6 character NES Code to an 8 character NES Code
This document was written by:
Tony Hedstrom t.hed@excite.com
This document explains how to convert a 6 letter NES
(Nintendo) Game Genie code into an 8 letter code.
Before I start, I should mention that most of the
time, an 8 letter code is better than a 6 letter
code, so if you have a 6 letter code that has some
glitches, or has some problems, there is a chance
that changing it to an 8 letter code will get rid of
the problems. But there is also the chance that
changing it to an 8 letter code will have unwanted
effects on the code.
Sometimes, a 6 letter code will cause more than one
effect (because it usually modifies more than one
address), but if you convert it to an 8 letter code,
it will only modify one address, so you may lose
some of the effects of the 6 letter code.
All I'm trying to say is that most of the time,
converting a 6 letter code to an 8 letter will make
the code better, but sometimes, it can make it worse.
On smaller games, changing a 6 letter code to an 8
letter code will sometimes make no difference.
Generally speaking, the larger a game is, the more
difference you will notice between a 6 and 8 letter
code.
OK, lets get started...
There are 3 ways that I know of to do this:
1) Try all 256 different possibilities until you find
the right one... That would take way too long.
2) Use a 6502 disassembler. This is probably the
most efficient method to use, but it's a little
bit complicated.
3) Use a hex editor. This is the method that I will
use in this example.
This is what you'll need:
1) A Game Genie code converter program (that changes
GG codes into hex codes). You can get one from my
website (in the "Download" section):
http://www.angelfire.com/games2/codehut/
2) The ROM of the game you want to hack
3) A hex editor. You can get a free trial version of
Hex Workshop here: http://www.bpsoft.com/
For this example, I'm going to use a GG code I made
for Megaman 3: NXTKGE start with infinite energy
tanks. Here's how to convert it into an 8 letter code:
1) Enter the GG code (in this case NXTKGE) into the
GG conversion program and write down the raw hex
code that the program gives you (in this case it's
40EC).
2) Add $10 (hex) to the code you wrote down. You can
use the Windows (or Mac) calculator to do this. To
find the Windows Calculator, click on Start/
Programs/Accessories/Calculator, then in the calc
window, click on "View" and click on "Scientific".
Also, make sure that you click on the Hex button.
If we add $10 to 40EC, we get 40FC. Write this
new number down.
3) Now, open up the ROM (in this case Megaman3.nes)
with a hex editor.
4) Find the hex address (the one with $10 added to it)
in the file that you just opened. In this case,
we're looking for 40FC.
5) When you find the right address (offset), write
down the two digit value that is there (in this
case, it's 48).
6) Now, find the address that is $8000 (hex) higher
than the one you just looked at. In this case,
we add $8000 to 40FC and we get C0FC. Remember,
you can use the Windows (or Mac) calculator to do
this hex addition.
7) Once you find the new address that is $8000 higher
than the last one (in this case it's C0FC), write
down the two digit value that is there (in this
case, it's 05).
8) Keep adding $8000 to the address and writing down
the two digit value at each new address until you
reach the end of the file.
9) Now, you should have between 1 to 16 (or more,
depending on how big the game is) two digit values
writen down. One of these, is the value that
you're looking for! Here are the values that I
found in this example: 48,05,00,21,E0,48,84,90,00,
00,FF,FC. Eliminate any duplicate values that you
may have. In this case, 48, and 00 are duplicates
(or triplicates), so I can delete the extras from
the list. This leaves us with: 48,05,00,21,E0,84,
90,FF,FC. Exit the hex editor, we won't need it
anymore.
10) Take your list of values and convert each one into
a Game Genie code using the GG code conversion
program. Here's how: Enter your original 6 letter
GG code (in this case NXTKGE) into the conversion
program. (I highly recommend using the GG code
conversion program that's on my website for this,
it's called "ggconvc". The address is at the end
of this document.) After you enter in your 6
letter GG code, you will see that below the code
you typed in, it gives you the hex code. In the
middle of the hex code, there is an empty box with
a "?" next to it (on the left). This is where you
type in the two digit values that you wrote down
before. When you type in one of the two digit
values in this box, it will convert it into an 8
letter GG code which it shows you in the "GG Code"
box. Do this for each one of the two digit values
that you wrote down and write down each new 8
letter GG code that the program gives you.
Here's our list of two digit values that we wrote
down before: 48,05,00,21,E0,84,90,FF,FC.
Here are the codes that we get from this list:
40EC 48 AF = NXVKGEAK
40EC 05 AF = NXVKGAIE
40EC 00 AF = NXVKGAAE
40EC 21 AF = NXVKGAPX
40EC E0 AF = NXVKGAEV
40EC 84 AF = NXVKGAKE
40EC 90 AF = NXVKGAEO
40EC FF AF = NXVKGENN
40EC FC AF = NXVKGEKN
11) Now take your new list of 8 letter GG codes and
try each one until you find the one that works
(in this case, it's NXVKGAEO).
Well, that's it. I hope this helps.
You can email me at: Tony Hedstrom t.hed@excite.com
Visit my website (The Code Hut) at:
http://www.angelfire.com/games2/codehut/