Random Access Memory (RAM) Types & Importance

•               DDR SDRAM, also called DDR or DDR1, is one of the more common types of memory found in desktop and notebook      computers. DDR1 RAM is capable of a maximum transfer speed of 3,200 MB per second. This is significantly faster than the older standard, SDRAM, but is slower than DDR2 and DDR3 RAM. DDR1 RAM is capable of a maximum transfer speed of 3,200 MB per second. DDR1 RAM is not interchangeable with SDRAM, DDR2-SDRAM, or DDR3-SDRAM. A computer that has DDR1 installed can handle only that type of RAM. The different types of RAM modules are keyed with tabs and notches, preventing them from being installed into incompatible motherboards. A RAM module should never be forced into an upgrade slot if it cannot be inserted easily

•                DDR2 is the next-generation DDR memory technology which features faster speeds, higher data bandwidths, lower power consumption, and enhanced thermal performance. DDR2 memory modules have basically the same dimensions as the DDR modules, but have different pin configurations, therefore DDR2 DIMM will not fit in the DDR memory slotDDR2 memory is the second generation in DDR memory. DDR2 begins with a speed level of 400MHz as the lowest available while the 400MHz speed is actually the highest speed for DDR1. Therefore, DDR2 picks up where DDR1 leaves off. It's a bit strange but due to different latencies a 400MHz DDR1 will outperform a 400MHz DDR2, but the advantage returns to DDR2 as soon as the speed reaches the next step 532MHz, which DDR1 cannot reach.

• The DDR3 components are twice as fast as today's highest speed DDR2 memory products. The main advantages of DDR3 are the higher bandwidth and the increase in performance at low power. The DDR3 SDRAM devices will offer data transfer rates up to 1600 Mbps (megabits per second).The supply voltage for the memory technology is being reduced from 1.8 volts for DDR2 to just 1.5 volts for DDR3 targeting a work day equivalent of battery time. The voltage reduction limits the amount of power that is consumed and heat that is generated in connection with the increase in bandwidths.

This image shows difference between DDR1,DDR2 and DDR3