Upgraded Z400 to W3690 show only 2 (maybe 4) cores instead of 6 cores

Hi,

I upgraded the cpu of a Z400 v2 machine to a W3690, previously it was using a X5570 cpu. 

Unfortunately, none of the tools I have show it using 6 cores:

CPU-Z: 4 cores

Thottlestop: 4 cores

Performance Monitor: 2 cores

HWMonitor: 4 cores

I did get a warning on boot up that the cooling fan was low performance for the cpu.  Could this be the problem or did I get a bad CPU or did I miss some type of setup step?

thanks in advance!