Are you suggesting connecting adjacent Pi's directly over GPIO? I've tried this before and it doesn't really work out very well. At some point, I ended up with

Are you suggesting connecting adjacent Pi's directly over GPIO? I've tried this before and it doesn't really work out very well. At some point, I ended up with the ground voltages going off and then everything was just borked. Plus, the speed of SPI, I2C, or bit-banging GPIO is several orders of magnitude slower than Ethernet. Communication over GPIO is a cool idea but ultimately pointless.