Hristo Benev wrote: > What if you boot with other kernel? > > If you have the same result maybe BIOS update is required for your server?! Hi thanks for the response BIOS is updated and current, if I boot to gentoo liveCD, I see the expected 4 processors. This server has indeed shown TWO processors using centOS xen-kernel before, but now after some time and upgrades I notice there is only one (again!). Is it as simple as BIOS in every case, or is there some other path to discovering the problem I can try? (I have done many many hours of forum searches and googling on this issue) Thank you