Out with the old...
Opening the Xbox-controller isn't that difficult as opening some other
game consoles and their accessories (I'm looking at you, Nintendo): just
unscrew a few standard Phillips-head screws and you can reach the internals.
The PCB revealed three main chips:
There's an USB1.1 hub made by Atmel especially for Microsoft (but aside from
a few descriptor-strings, not too different from a normal hub), a large chip
made by ST which is the main Xbox-controller-controller and a small 8-to-2
mux. The mux is needed because the Xbox has a whopping 12 analog channels
(remember: in the Xbox-controller most of the buttons are analog too!) and
the ST-chip only has 8 A/D-inputs.
At first, I was hoping the controller was reflashable, so I could just modify the firmware a bit and be done. As soon as I saw the inscription 'MSFT' on the chip, those hopes sank, and after looking up the datasheet of the IC, I knew that the chip kept it's firmware in unflashable mask ROM. No chance of modifying anything there. So I decided the chip had to go.
For those interested in how to remove such a behemoth of an IC, some pics.
First I cut the pins using a sharp knife off three of the four sides of the IC.
If you repeat this, be sure to point the point of the knife towards the IC, and
not towards the PCB. If you damage anything on the IC, no problem; if you
accidentally cut a trace on the PCB it can take a lot of time to repair it, though.
Then, make use of metal fatigue and bend the chip a few times so the remaining
pins break too. Finally, use a soldering iron and some soldering wick to clean off
the pads, and the PCB looks like the IC never was there in the first place:
Now, how are we going to replace the missing controller?