Each F@H_core only supports a single CPU 'c'os its a single threaded application ... but if you follow the instructions on the F@H site, then you can run 2 copies ( 1 on each CPU ) simultaeneously ... they will both run at full rate .. and will therefore way outperform a 3GHz P4.
And dual XP3200+s would be even better :-)
They need to get an AMD64 build on the scene !