I have a Dual-Socket workstation, but I only have one CPU at the moment. Would adding another CPU help in the editor? I recall that most of the epic team use Dual Xeons, but I am not sure if that is just for Visual Studio. Thanks.
As you can see there are no answers to your simple question. It is because of this terrible UE support on forums but also here in answer hub.
But nevermind. Maybe my little experience with Xeons will help you.
As I was asking people the same thing about this issue, ordinary Xeons, which you can purchase from official store will work if you choose properly your HW and your OS will recognize both processors.
The problem can occur if you buy the ES Xeons (engineering samples) from ebay or so…
Some of the softs like 3ds max with vray are compatible with them but it looks like that UE is always working with only one CPU during building light.
I hope it will be fixed in the future.