If you buy value ram often then you'll run into those a lot. A Corsair 1gb value ram here is single sided. That was bought just prior to upgrading the cpu on the last board in order to run in dual channel mode. The AMD models prior to the Atholon XP3200+ didn't suport dual. After the cpu was installed a pair Corsair xms series 512mb dual sided performance dimms suddenly found their way here.