Threads and mulitcore processors.
I do not profess to be a either a hardware or software expert. I know Haiku is threaded OS. And I know when I run Haiku on my single core Atom there are two virtual cores. When AMD realised its "cheap" 6 core and then recently its "cheap" 8 core there was talk that most software couldn't make use of all those extra cores. But I am right in thinking that Haiku would just soak up (as needed) and exploit all that extra grunt because of its architecture. Not sure what you would do with all that extra power.