Guys, unless you can get them from a genuine retailer DO NOT buy the e5 - 2651 v2 CPU's. I brought 4 of these CPU's all from different sellers on ebay and all of them were fakes.
After doing some research I found that a Chinese company "acquired" 1000's of engineering sample 2651 v2's. They skimmed the surface and reprinted them in black in without "engineering sample".
To anyone looking these CPU's will appear to be genuine, however once you get them home they perform erratic and very slow, worse than a core 2 duo. Even with underclocking I couldn't get any of mine to be stable for more than a few minutes. Mining is totally out of the question.
To make matters worse it was an absolute nightmare trying to get my money back, 2 sellers refused the refund and it took weeks of email disputes and phone calls. The tech support center ruled in favour of the 2 sellers and I had to ring Ebay's head office and forward my research, it was only then that they actually issued me a cheque direct from ebay! They said they would remove the 2651v2's from ebay but having looked today loads of new sellers have popped up selling the same CPU's.
2 of the dud CPU's I got from ebay all had this printed on them....
INTEL(R)XEON(R) E5-2651 V2
SR19K 1.80GHZ
COSTA RICA
33378986 (E4)
The others had the same but with the following serial numbers:
34108638
3351B997
Both Chinese sellers had 33378986, one thing i did notice was on one of the auctions the last 4 digits had been pixellated out.
34108638, this one came from the USA (the seller said it was from his personal workstation). The last one was 3351B997 and the seller was based in Latvia.
As it stands I don't know if we can use the serial numbers as a reliable indicator. I was hoping that the fakes would all have the same serial number so that we can avoid.
Anyway, I really hope my findings prevent anybody else from being scammed. Please, be careful out there, so many scams seemed to be directed towards miners.