Red Hat Virtualization supports multiprocessor systems and allows you can run Red Hat Virtualization on x86 architectured systems with a P6 class (or earlier) processors like:

With Red Hat Virtualization, 32-bit hosts runs only 32-bit paravirtual guests. 64-bit hosts runs only 64-bit paravirtual guests. And a 64-bit full virtualization host runs 32-bit, 32-bit PAE, or 64-bit guests. A 32-bit full virtualization host runs both PAE and non-PAE full virtualization guests.

The Red Hat Enterprise Linux Virtualization kernel does not support more than 32GB of memory for x86_64 systems. If you need to boot the virtualization kernel on systems with more than 32GB of physical memory installed, you must you must append the kernel command line with mem=32G. This example shows how to enable the proper parameters in the grub.conf file:

title Red Hat Enterprise Linux Server  (2.6.18-4.elxen)
root  (hd0, 0)
kernel   /xen.gz-2.6.18-4-el5 mem=32G
module   /vmlinuz -2.6.18-4.el5xen ro root=LABEL=/
module   /initrd-2.6.18-4.el5xen.img

PAE (Physical Address Extension) is a technology that increases the amount of physical or virtual memory available to user applications. Red Hat Virtualization requires that PAE is active on your systems. Red Hat Virtualization 32 bit architecture with PAE supports up to 16 GB of physical memory. It is recommended that you have at least 256 megabytes of RAM for every guest you have running on the system. Red Hat Virtualization enables x86/64 machines to address up to physical 64 GB. The Red Hat Virtualization kernels will not run on a non-PAE system. To determine if a your system supports PAE, enter the following commands:

grep pae /proc/cpuinfo 

The following output displays:

flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 mmx fxsr sse syscall mmtext 3dnowext 3dnow up ts

If your output matches (or is similar to) the above, then your CPU supports PAE. If the command prompt displays nothing, then your CPU does not support PAE.