Why Core-Based Licensing Matters for Performance Tuning
If you don't license all of your SQL Server's CPU cores, you need to pay particular attention to your server hardware.
Say you're using an HP DL580 with four CPU sockets, each of which has a Xeon processor plugged in with 10 cores. That's a total of 40 real cores, or 80 logical processors if you've enabled hyperthreading.