Hey I found this at bunnie's website AKA the buy who wrote "Hacking The Xbox" very good book might I add.
Aerogel Capacitor
Did anyone else notice the aerogel capacitor on the Xbox? There is a 1 Farad 2.5V cap on there at location C7G10. What...the heck. When I unplug my xbox for longer than a few minutes, I still have to reset the time. Why not use a battery? It's not like the Xbox is going to outlast the shelf-life of a lithium battery. Maybe I'm wrong, but I thought aerogels are relatively new and expensive...yeah, I'm probably wrong. I've never priced out an aerogel, so mabye they are cheap. But damn, that's the first I've ever seen an aerogel in a consumer electronics product. A brief analysis of the rationale for this capacitor is provided at this forum link.
Also, there is a resistor that's not populated at R7R4 on the backside of the motherboard. It seems to connect the FLASH ROM's WE line to the MCP. Perhaps by jumpering this you can enable in-system ROM flashing...of course, you'd need to find software that does it first.