I too would be interested in playing around with more processor to processor interconnects. Just for fun I built a 16 way SAMD21 board that used the serial int

I too would be interested in playing around with more processor to processor interconnects. Just for fun I built a 16 way SAMD21 board that used the serial interconnects to make a hypercube arrangement and it was very cool to play with. It would be possible to build an interconnect over PCIe, but of course it might just be better to use a 10g ethernet PCIe interface chip for each node and a local to PCB network.