How to add a Gecko Code to the Dolphin Emulator
When adding a Gecko code you'll need to copy and paste your code into a text file instead of adding them the same way as Action Replay codes. To find the appropriate text file go to the game you want to add a Gecko code to and right click it. Select "Properties" the same way you do for ActionReplay codes in the previous guide.
Select the Gecko Codes tab and at the bottom (shown in the screenshot above) you'll see a button that says "Edit Config". Click this and it will bring up a notepad file (usually) with nothing in it. Below are a few examples of the format that you're going to want to use when adding codes.
$Name of Code
$Name of Code 2
The $ symbol goes in front of the code's name and the code is input directly below. If you need to, copy and paste the format provided above into your text file and rewrite it to what it should be.
In the example below I copy and pasted some codes from the Wind Waker file that are for Action Replay. These codes were built into my Dolphin emulator and most likely yours as well for this game. They use the same exact format that the Gecko codes use and are a good teaching aid despite being Action Replay codes.
# Add action replay cheats here.
$Never Lose Health
$Can Carry 5000 Rupees
Now, onto real Gecko codes. One of the only examples online I could find of Gecko codes for Gamecube is Super Mario Sunshine. They have a widescreen code as well as an FPS code, both of which are linked below. You'll notice that they do indeed use the same format as the Action Replay codes above. There is an $ in front of the code's name and then the code is entered below.
Further down this page I have a notepad file which shows you how it's formatted inside of the file itself.
$60FPS (NTSC-U) [gamemasterplc]
Assuming that you did everything correctly your codes should appear in the "Gecko Codes" list when you save and close the Notepad file. You'll need to check the box with the code to enable it still but that's it. At this point all that is left is to log into the game and make sure your code is working, if it is not then you may have input it incorrectly or the code you're trying just doesn't work.
If you'd like to add some Action Replay codes for your game, head back to the How to add codes to the Dolphin Emulator page for more information on them specifically.