Although we're a bit off-topic here, I wrote a post on the other thread about expected DMIPS for Espresso and other gaming CPUs, and even at 1.25GHz, Espresso should perform about 35% better than Xenon in Dhrystone. Now, of course that doesn't incorporate SIMD or anything like that, but still interesting.
That doesn't seem quite right to me. SERDES is designed to get high bandwidth out of few wires or traces. There's very little cost to running wires over an MCM (indeed that's pretty much the entire reason for the CPU and GPU being on an MCM), so a SERDES interface seems like massive overkill. On the motherboard, though, where traces are expensive (and given the use of a 64 bit memory bus, it seems Nintendo is intent on minimising the number of them), a SERDES is a sensible choice. Especially if, as Marcan apparently claimed, the actual gamepad image compression is handled on a separate chip, which means you need to transfer uncompressed video and audio across there.