I recently came into possession of an old Dell Precision T3610 workstation and promptly installed Proxmox to add it to my Proxmox cluster. After performing some ludicrously silly RAM and storage upgrades (how about 96 GB of DDR3, plus a 13-disk array of 500 GB SSDs?), I decided I wanted to max out the CPU as well.

The Precision T3610 shipped with an Intel Xeon E5-1650 v2. According to the linked Intel product page, this CPU uses the FCLGA2011 socket. Easy enough, I thought to myself. Just find the best CPU that supports FCLGA2011, make sure you have the latest BIOS installed, and everything should be all hunky dory. So I did some research and landed on the Xeon E7-8890 v4. It’s several years newer than the E5-1650 v2, has a whopping 24 cores (and hyperthreading bumps it to 48 logical cores!), and can support having not one, not two, but eight of itself installed in a single motherboard! Most crucially, the Intel product page says it uses the FCLGA2011 socket. When I stumbled across one of these monsters on eBay for just $15, I snapped it up.

Cue my massive shock and disappointment when, a few days later, I found myself unable to install the E7-8890 v4 in my T3610. The new CPU, despite being the same physical size as the old CPU, had extra contacts on the bottom and had a different physical keying. What? I thought Intel said this was the same socket!

Some amount of research later, I discovered that Intel’s LGA2011 socket has many variations. One of these variations is also called Socket R (or LGA2011-0). The T3610, and by extension the old E5-1650 v2 CPU, uses Socket R. The newer E7-8890 v4, meanwhile, uses a different variation called Socket R2 (or LGA2011-1). As if this wasn’t confusing enough, there’s even a third variation of the LGA2011 socket! I’ll refer you to the Wikipedia page for more info on that.

This is obviously not a great naming scheme. Why not use unique numbers for each version of the socket instead of tacking on a suffix? But the real kicker here is that Intel itself doesn’t seem to be able to keep up with its own naming scheme! It appears that its CPU specifications pages refer to all variants of the LGA2011 socket as FCLGA2011. This leaves folks like myself wondering what went wrong when their new-to-them CPUs don’t fit in their motherboards.

So where does that leave me? Well, I now have a fancy paperweight. I could have returned the CPU, but return shipping costs would have been half of what I paid for the CPU itself, so I’m hanging onto it for now in case I ever come into possession of a server with a Socket R2 motherboard that could use a nicer CPU. At least it wasn’t a super expensive CPU, so all in all, this isn’t the worst learning experience ever.