I think core communications slow performance. If cores do not share data with each other while running or share libraries, I do not think there is a Maximum core count.
When I assembled my cluster, I had not considered Security. The used computers I purchased through e-bay had no WiFi, and only one Ethernet outlet that I used to connect to the switch. I write and test code on a separate computer, I then transfer to my cluster using a USB flash drive.
Politicians select "Unemployment Numbers" & "Stock Market" to support their climes. They are to far removed from the "Homeless" to see poverty. And they will not "Balance the budget" or pay on the "National Debit". State pork keeps getting them elected.
Before investing to much, buy 2 computers of interest. Assign one as the controller and the other as the slave. An Ethernet switch and 2 cables to connect them together. That way you can verify an Operating System and computer are compatible. Learning along your journey.
A few yrs ago I payed around $125 per computer. Now $75 to $100 would be typical, I expect an SSD & 8gb of memory for that price. The rack, power strips, power plugs, spacing dowels, Ethernet switch & cables, add to the cost. I also have a remote switch for power, so I can control boot up. Also GFI.
