a p4 is a single core processor. it means there is a single processing unit (core) in it. in dual core processors there are 2 processing units, i.e., 2 cores. core duo was the first series by intel, and core 2 duo is a next model in dual core processor by intel. AMD also has its dula core processor series X2 which were released before intel by didn't get much recognition. Core 2 Quad is a 4 core core processor that is there are 4 cores or processing units...