They are going to use ethernet in this version - been cooking up an alternative that is much less cable intensive! The dark grey boxes in the bottom are 48 port switches. Have had to get bootless ethernet cables to make them fit as you’re right - there isn’t much space! Getting this many boards to join to a standard WiFi router is a bit of a non starter. I will be using one vim to provide DHCP /DNS service to the rest and bridge to the WiFi for connecting to the internet
ROI for the whole thing is not at these spot prices as bitcoin has just tanked and done the usual and taken the alt coins with them as well. So right now its something like 2 years to get the investment back (including electricity) but conservatively expect that proves to recover to the point where ROI is something like 6 to 12 months which is comparable to ASIC miners
Also worth saying I’ve got other SBC based miners that have been running for ~1.5yrs and they are still going strong. Can always change coin if needed. But this approach has been the advantage of longevity as power costs are much lower than servers so difficulty can go up much higher before it becomes unprofitable to mine. A used servers does have a much lower cost of entry though.