Index: /trunk/src/VBox/VMM/CPUM.cpp
===================================================================
--- /trunk/src/VBox/VMM/CPUM.cpp	(revision 20156)
+++ /trunk/src/VBox/VMM/CPUM.cpp	(revision 20157)
@@ -508,4 +508,7 @@
         if (pVM->cpum.s.enmCPUVendor == CPUMCPUVENDOR_AMD)
         {
+            /* Legacy method to determine the number of cores. */
+            pCPUM->aGuestCpuIdExt[1].ecx |= X86_CPUID_AMD_FEATURE_ECX_CMPL;
+            pCPUM->aGuestCpuIdExt[8].ecx |= (pVM->cCPUs - 1); /* NC: Number of CPU cores - 1; 8 bits */
 
         }