> Nobody is putting x86_64s on tiny boards embedded
in vending machines
> talking to GSM modems. (something I'm in the process of doing right
> now!)
 OK, but why do your GSM modems need to be talking to 2+ interlinked
 cores rather than one core that is 2+ times as fast? What are you doing
 with them that makes controllling them with a single fast core
 impractical? 
 ...
 Then it dawned on me: I had 144 very simple cores that are VERY cheap,
 less than fourteen cents apiece at the single-unit quantity price:
 implement a bit-banged SPI controller in one of those cores! ...
 In this case, it's not all about distributing "processes" across
 multiple processors, but "functionality", where some of those
 functionalities might be implemented in purpose-built, rather than
 general-purpose hardware on more traditional microcontroller designs. 
 
 That sounds like the Transputer model -- there was quite a diversity of
 devices accessible via the standard serial links: I/O, storage,
 graphics, networks, etc.