Just an update on my progress...
I now have 4 pads working nicely on both 1.0 and 1.6 xbox's.
TMaul has also tested my single pad code on his 1.2/1.3 box and reports it working fine - so I see no reason why it won't work on all versions of xbox.
I'm also putting together some nice code to interface to all of this.
Things still to do....
- tidy a couple of joypad related things up
- keyboard/mouse support
- xbox remote support
- memory unit support??? (possibly - depends how much time I get and if I manage to get hold of a memory unit)
Everything is progressing very nicely though

Carcharius