HP Z620 not booting with Xeon E5-2667V2 CPUs?

Hi,

I bought second hand 2x Xeon E5-2667 V2 to upgrade my 2690 V1 and my HP Z620 refuses to post / boot. Nothing happens at all for 20 seconds then the CPU fan starts spinning cold air like crazy. 

I have the last HP Z620 Bios 3.91

In the Bios American Megatrends indicates 2.15.1229

This Xeon CPU E5-2667 V2 is indicated as compatible with the HP Z620. 

I tried booting with both CPU, then with only a single CPU trying both in the main slot.

Perhaps it's not compatible on ALL revisions of the workstation? Or is there anything else I can set to make these CPU work? 

Thanks!

xberg