I haven't tried Linux 2.2, but FreeBSD SMP should be comparable. I've got FreeBSD 3.1-RELEASE running on a dual-400MHz Celeron box (*not* overclocked), and it screams.
Side note: while it was worth it when I built the box, dual Celerons make less sense now, as the price differential for two CPUs (Celeron vs PII) is on the order of a couple hundred dollars. It's probably now worth the extra cost to get a 100MHz FSB (when you don't overclock) and a 512KB cache (even if it isn't zero-wait). These are important for SMP.
Re:SMP support? (Score:1)
Side note: while it was worth it when I built the box, dual Celerons make less sense now, as the price differential for two CPUs (Celeron vs PII) is on the order of a couple hundred dollars. It's probably now worth the extra cost to get a 100MHz FSB (when you don't overclock) and a 512KB cache (even if it isn't zero-wait). These are important for SMP.