Replaced E5-1620 V2 with this E5-1660 V2 and saw big improvement
This E5-1660 V2 CPU replaced the stock E5-1620 V2 CPU in my Mac Pro (late 2013). It has 2 more cores, but runs at the same 3.7GHz. I can't tell you how much smoother the computer runs. The two extra cores help by 50% on the 300+ tasks running on the Mac when it is "idle". I recommend this upgrade to any who are capable of doing it. I recommend this CPU to anyone who wants a high clock speed and higher core count while not breaking the bank.