It's likely a setting in the BIOS.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003945

On Tue, Dec 22, 2009 at 9:12 AM, Randy Clarksean <rclarksean at arvig.net> wrote:
> Ok .. just purchased a used Dell PowerEdge 6850 on Ebay.  4 CPUs at 3.16
> GHz.  I purchased it to make a computational box out of it ... wanting the 8
> cores and lots of memory.
>
> Now ... I put VMWare ESxi 4.0 on it and was installing a 64 bit version of
> Scientific Linux.  During the install ... it tells me that I can not install
> a 64 bit version ... and that I should install a 32 bit version.
>
> The CPU details are listed below ... I THOUGHT these were 64 bit CPUs ...
> did I mess up?
>
> 3.16GHZ INTEL XEON-MP 667MHZ SOCKET 604 1MB SL84U
>
> Thoughts and comments welcome.  Thanks in advance.
>
> Randy
>
>
>
>
> _______________________________________________
> TCLUG Mailing List - Minneapolis/St. Paul, Minnesota
> tclug-list at mn-linux.org
> http://mailman.mn-linux.org/mailman/listinfo/tclug-list
>