Im running a Dual too, and to my knowledge there -was- a patch for kernel-2.2x's called Pset for setting processor affinity like NT4/NT5 knows. Now only the
cached page remains. The utils Ive found, the patch not.
Kernel-2.4x has better chances look at http://www.uow.edu.au/~andrewm/ and http://people.redhat.com/mingo/.