go into bios and load optimized defaults.
then in windows go to power management and set it to high performance.
cpu-z is defiantly misidentifying the cpu as its M1 stepping not D7
Intel(R) Xeon(R) CPU E5-2665 has the 206d7 cpuid.
but i also see it is listed for the 3820http://ark.intel.com/products/63698/Intel-Core-i7-3820-Processor-(10M-Cache-up-to-3_80-GHz)#infosectionadvancedtechnologies
so either cpu-id is making a mistake or your bios is. i recommend you swap your old cpu back in if you have it and update the bios to the latest version than install your new cpu.
and dont forget to load optimized defaults or the cpu wont be identified properly. (if you didn't do it before then thats likely the reason its being misidentified now) so do this befor you run a bios update.