an X2 isn't an athlon 64. It is an Athlon X2. Athlon 64 are SINGLE core only...
I think back in the day AMD made a few CPUs named Athlon64 X2. But they dropped the 64 bit since really, every processor in the last few years has been one. Intel integrated the AMD64 architecture long ago, and AMD felt it was no longer a useful marketing gimmick (at first it was, since they were the only ones to have 64bit support).