Thread issue in windows with Precision Tower 3620

Hi, I have a dell precision tower 3620 and I recently upgraded the processor to an i7 7700, and I noticed that windows detects 4 cores, but only 4 threads, when the processor has 8 threads. Previously I had a xeon e3 1225 v5, 4 cores, 4 threads. I've already tried changing the BIOS version and changing the hyperthreading options (all running on windows 10 64bit)