Why are not all CPU cores used?

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If you check in the Task Manager on the Server and find that it looks like this:


Why are not all cores used? If we make som further investigations like SQL Server properties:


SQL Server has detected all 8 cores and if we then check the Processor settings:


All cores will be used, nothing that explains the behavior.

If we than check the dmv:s we get that 4 cores is offline, what can cause that?


Finally we check the SQL Server log and in one of the startup messages you can get the solution:

SQL Server detected 8 sockets with 1 core per socket and 1 logical processors per socket 8 total logical processors; using 4 logical processors based on SQL Server licensing. This is an informational message; no user action is required

In this case we can change the vmWare setup and give the VM 2 sockets with 4 cores per sockets instead, then SQL Server can detect and use 8 cores.