> I don't buy the speed argument. In a modern PC, many things are pluggable. PCI express can transmit up to 30 GB/s, IIRC. Even CPUs and RAM are modular. If there was such a benefit from soldering them together, I'm sure we would be seeing more integrated systems.
The issue between the CPU and memory isn't throughput (the vast majority of operations are > Furthermore, the modem part of many smartphones is already a black box that is heavily isolated from every other component. It's basically just hooked into a bus, and connected to microphone, speakers, and antennas, and doesn't necessarily interface that much with the CPU.
This is partially true. The CPU still needs to control the radio, and they're constantly feeding each other data. You might want to send the audio data through a DSP for audio processing. The microphones/speakers will be shared between the two, and probably go through a codec. Also, Qualcomm radios and CPUs are pretty tightly coupled. If you want to do CDMA for the US (they seem to have patents on all of the CDMA tech) then you need to use a QC radio, which means that you need to use a QC processor, a QC codec, ... (Source: I used to work on audio firmware at RIM.)