The thing is with AMD the 61xx series are faster crunching core to core VS the newer 62xx and 63xx CPUs.
From what I understand the newer CPUs have kinda, sorta, kinda, have HT enabled.
I'll have to search the exact terms, two cores use one "something or other" where as the 61xx had one "Something or other" per core.
That"s why the 61xx are faster, you need 12 62xx cores to equal 8 61xx cores
 
Look in the BIOS for "fast" or performance computing setting and make sure it is on or set to performance.
There is a way to do some overclocking on 62xx and 63xx CPU Opteron servers.

HK-Steve
Yeah, AMD have done something wrong,
These are AVX 1.1 instructions maximum for the cpu's... best I can do in this server..
Better than nothing... 

I have the same issue on my AMD Rigs as well.

Just picked up a HP DL580 G7 server yesterday.
Has 4x CPU's and 128Gb of ram, 32Gb per CPU. Currently has E-7540's installed. 6 Cores @ 2.0Ghz. Turned HT off for now.
 
With the Xeon @ 2.0Ghz compaired to the AMD @ 2.6Ghz, The Xeon is faster on all tasks so far..
 
Just ordered 4x E7-4870's. 2.4Ghz with 10 Cores each. Looking forward to these being installed next week.