I own an e7-8880 CPU and also purchased a motherboard model x79, but it doesn't fit into the socket.
I own an e7-8880 CPU and also purchased a motherboard model x79, but it doesn't fit into the socket.
Those chips aren't suitable for your intended use. The Xeon E7 processors are designed only for large servers such as the PowerEdge R930. Since they lack built-in memory controllers, they won't function on standard motherboards. You'll need a Xeon E5 v0 or v2 series processor for that platform. (x79 boards aren't compatible with Haswell or Broadwell chips.)
Likely none of these. The 8xxx CPUs use socket 2011-1, unlike X79 (socket 2011) or X99 (socket 2011v3). These chips are built for eight socket monster servers, featuring a unique IO layout on the socket to enable communication between them, which explains the variations.
They mentioned E5 v1 and E5 v2 fit X79 E5 v3 and E5 v4, but those don't work with the ones you described. I noticed many budget E7 CPUs were available before, probably because few people could actually use them. The market for E5 dropped so much, so you might want to stick with one of those alternatives for the X79 slot and consider skipping the E7.