Is my MacPro 5,1 single or dual socket?
Take the side off &amp; look ;)
A 6-core is probably a single socket, a 12 would be a dual.
You can also tell from About this Mac &gt; Memory.
Dual socket has 8 RAM slots, single has 4.
single…

dual…

The sockets are on a daughter-card which slides out &amp; is replaceable/interchangeable.
Image from OWC