yes in the reality all cores are floated with any kind of stuff all the time.
in an benchmark only 1 program make a load.
i also think that the bulldozer beat the intel cpu if you run all stuff in the same time.
i for example i do not open up 1 browser windows i do have 60+ browser windows.
you can beat any cpu only with the browser just open up 200 of them and do some stuff.
the "singlecore" performance really only care in benchmarks.