DDR1 RAM; also called the DDR Double Data is capable of making 2 transfers of data per differential clocks
. DDR2 RAMs are faster than the former as they include speed limits that start off with 400 MHZ which is the lowest speed as in comparison to the former that offers the maximum speed of 400MHz. However one strange thing to consider is that if you are looking for 400MHz of transfer rate then DDR1 RAM out performs DDR2 RAM as they function on different latencies, however this benefit gets surpassed by DDR2 RAM when it picks up speed and is able to perform best even at 532MHZ, which is next to impossible for DDR1 to reach. Comparing this to DDR3, it begins with 800 Mbps and is able to perform well till 1600Mbps with the speed of 2000 MHz, which is simply phenomenal as in comparison to the other two. Another advantage is that the voltage consumption of DDR3 is much lower. It uses 1.5V as in comparison to 1.8 V of DDR2, this leads to lower heat generation by system which actually keeps the function cool. All in all one can simply wonder at the technological advancements that are prevalent in all arenas that are leading to increased efficiencies all along.