Has Intel unified the socket for desktop and server processors?

Question

Processors

I sit, I choose the server. I see, for example, HP ProLiant DL120 G7, you can choose from Intel Xeon E3 product family, Intel Core i3, Intel Pentium, Intel Celeron. And this is not the only example of a branded server, where both Xeons and Pentiums and Celerons and Cores are represented in the choice of processors at the same time. How can this be? There, depending on the choice, different motherboards are supplied, or did common sense finally win and Intel made a single socket? I used to follow the development of processors and sockets, in recent years I somehow forgot, who knows - clarify, plz. Of particular interest is the question of whether I can take, for example, with Core i3 or Celeron, and in the future, if the need arises, buy in a store and put there, say, Core i7 (missing in the original choice).

Answer 1

As if the easiest source, except for ark.intel.com ;)
Modern (Sandy Bridge) Xeon E3 on socket 1155 (SP), older models - on 1356 (DP) and 2011 (MP), Older models (Nehalem\Westmere ) on 1156, 1366 (DP), 1567 (MP)
According to DL120G7, I can tell you what is in use.