This is pretty much what the Raspberry Pi does, so we should all switch to that :-) There is ROM (as far as we know) in the GPU which instructs it to read the

This is pretty much what the Raspberry Pi does, so we should all switch to that :-) There is ROM (as far as we know) in the GPU which instructs it to read the CPU firmware from the SD card, and then boots up the machine. Unfortunately neither firmware is open source or well documented, so you still can't really trust it.