The
3900 is based on
Zen 2 architecture while the
E5-2651 v2 is based on
Ivy Bridge.
Using the multithread performance as a reference, the 3900 gets a score of
620.2 k points while the E5-2651 v2 gets
426.2 k points.
Summarizing, the
3900 is
1.5 times faster than the
E5-2651 v2. To get a proper comparison between both models, take a look to the data shown below.