You may find this a fascinating read. It's regarding how SQL Server has it's own threading scheduler to bypass the Windows scheduler. When ran on a machine with HyperThreading enabled it will only use 50% of the CPU, I guess they're going after CPU Cache utilisation.

It's really hard to find a decent article on the subject, here's two of the best I've found. https://www.mssqltips.com/sqlservertip/4403/understanding-sq... https://docs.microsoft.com/en-us/sql/relational-databases/th...