Will Gecko OS load this up?
If it doesn't boot through the Disc Channel, I think that you might need to downgrade the MIOS first.
If you already have the GameCube Action Replay, try booting it with GeckoOS. If you still need to buy one, Datel has newer versions which should be compatible with the current firmwares. However, keep in mind that you will not be able to create/enter your own codes with it.
I don't have one right now so I can't test it. Does Datel sell versions compatible with 4.0?
I thought that they did. I'm guessing that you could E-Mail their customer service and ask them.
Do not bother to buy a newer action replay for GC. I would just wait for a new gecko OS with GCN support.
No gecko OS cannot load a GC action replay because the MIOS is a software thing so Gecko OS cannot get around it.
just get a usb gecko instead and use wiird cheats
You need MIOSv4 to load up the old Action Replay (1.14b or older). The new AR's can be loaded on MIOSv5, but I'm not sure about MIOSv8.
MIOSv6 can be passed by the ones on sale at their website,
v8 hasn't been beat yet.
I have AR v1.14 and it boots up on my Wii without a problem, however my Wii is chipped and the AR 1.14 that it boot is a copy. Surprisingly it will not boot an original AR disk.