LS-DYNA most definitely will make use of both CPUs (as long as you specify in the keyfile). The implicit ANSYS package is (1) license dependent (as an "add-on" package) and (2) solver dependent (see help file on the parallel processing guide) and can be activated by issuing /CON,NPROC,2. If you issue this command with all ANSYS defaults you will still only have access to one CPU. Same applies for windows/linux/unix machines I believe.
Cheers,
-- drej --