Both models
E5-2651 v2 and
E5-2660 v2 are based on
Ivy Bridge architecture.
"Ivy Bridge is the last Intel microarchitecture for which there is official driver support for Windows XP . It is made under 22 nm Tri-Gate transistor (""3D"") technology and is basically a Sandy Bridge shrink. It has PCI Express 3.0 support and RdRand instruction for security tasks."
Using the multithread performance as a reference, the E5-2651 v2 gets a score of
426.2 k points while the E5-2660 v2 gets
459.3 k points.
Summarizing, the
E5-2660 v2 is
1.1 times faster than the
E5-2651 v2. To get a proper comparison between both models, take a look to the data shown below.