Alle SME Versions older than 5.6 only Pentium III as SMP.
Newer Pentium IV and Xeon-CPUs only with Kernel 2.4. (SME 5.6) in SMP.Mode ( btw., Haperthreading, looks nice; 4 CPUs with two "newer" Xeons)
But you can use "newer CPUs" on every SME-Version in UP (Single-Processormode).
Greeting Michael