We’ve been putting Red Hat Advanced Server on some machines at work. “Normal” installations include three types of kernel: “enterprise”, SMP, and plain. (Enterprise is SMP and “bigmem”, or support for >4G RAM.)
The enterprise kernel didn’t seem to be working on our IBM eServer xSeries 445s, though. We added two processors (to make the total four) but the OS still recognized only two. We eventually called Red Hat’s technical support, which quickly pointed us to the answer: there is a special kernel just for the xSeries 440s.
Weird, huh?