i chipped about 8 xboxs using the smartx chip, and the bios you need is dependant upon the version of xbos you have. xbox version 1.6 are different to version 1.0 - 1.5
up to 1.5 you need executer 2 bios 4983
and 1.6 and 1.6b you need mx8 or mx8plus
it's been a good 6 months since i did one, so memory is not so good.
i'll try and find them bios's but can't post them cos they are illegal bios's. (m!crosoft laws)
its a 1.5 box, all that i can get from this chip is a startup screen with the 4 options i mentioned, im too scared to do anything though as im on the last level of halo and its stored on the hdd and if i lost that id cry lol