title: CPUID on multiple cores/NUMA
body: <p>I am working on CPU detection and general environment detection code for my hobby OS. Is there ever a case where CPUID needs to be called multiple times? That is if the system has multiple cores, does the OS need to call CPUID on each core? Same for NUMA.</p>
  
  <p>Both the <a href="http://support.amd.com/us/Embedded_TechDocs/25481.pdf" rel="noreferrer">AMD</a> and <a href="http://www.intel.com/content/dam/doc/application-note/processor-identification-cpuid-instruction-note.pdf" rel="noreferrer">Intel</a> CPUID manuals are unclear on this. There is an article on the osdev wiki that mentions calling CPUID called <a href="http://wiki.osdev.org/Detecting_CPU_Topology_%2880x86%29" rel="noreferrer">Detecting CPU Topology</a>, but to my reading was not clear as to when and how many times CPUID needs to be called.</p>