Well, I can't say for sure the reason why it doesn't see all cpus, but I do know a P-III system is not going to support virtualization technology, so you would never be able to run windows guests on it. Only systems sold in the last year or two support VT. And motherboards that do support it are fairly cheap - starting in the $60 range. Anywho, have you tried KVM instead? -----Original Message----- From: centos-virt-bounces at centos.org [mailto:centos-virt-bounces at centos.org] On Behalf Of Bryan A. Ignatow Sent: Thursday, June 03, 2010 10:27 AM To: Discussion about the virtualization on CentOS Subject: [CentOS-virt] Xen 3.1.2 on CentOS 5.5 doesn't see all 4 CPUs Hello all, I've been digging around on this for a few days and I have not come up with a solution. I have a Compaq ProLiant DL580 (G1, the old tan Compaq) with 4 x 700MHz P-III CPUs and 11GB of memory. I've loaded CentOS 5.5 with Virtualization (Xen) + KVM and patched up to current (full KS packages file list at the end). When it boots, Xen only detects a single CPU as shown in the xm dmesg output (full output and the end): (XEN) Detected 701.650 MHz processor. (XEN) I/O virtualisation disabled (XEN) CPU0: Intel Pentium III (Cascades) stepping 04 (XEN) Platform timer overflows in 2 jiffies. (XEN) Platform timer is 1.193MHz PIT (XEN) Brought up 1 CPUs [...] (XEN) Dom0 has maximum 1 VCPUs The system shows all 4 CPUs when booted outside of Xen. Any ideas on Xen options or anything I can try to see if I can get all 4 CPUs? Thanks, Bryan