Few days ago I had explained how to find the number of Physical CPUs installed using third party tools. Just a while ago, I figured out that using sys.dm_os_sys_info DMV that information can be obtained far more easily. I executed the following query on a server having 3 dual-core CPUs on it.
SELECT cpu_count, hyperthread_ratio, cpu_count /hyperthread_ratio as [Physical CPUs] FROM sys.dm_os_sys_info
As expected the DMV reported the information accurately and here is the output. Very useful.
However even this DMV does not detect quad-core CPUs. I tried it one of the servers that I support. As of now, CPU-Z holds the upper hand in detecting the Physical CPUs.