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Difference Between DDR2 and DDR3

dram_ddr2_512DDR2 vs DDR3

DDR3 is the memory that is expected to replace the current DDR2 memory modules that we are using today. Continuing with the trend that DDR2 started where the system bus runs twice as fast as the memory clock, with DDR3, the system bus runs four times faster compared to the memory bus. This means that with the current memory technology, systems using DDR3 memory modules can achieve bus speeds that are twice as fast as systems using DDR2 memory modules. Comparing a DDR2 and a DDR3 that are running at the same memory clock speed, the DDR3 module can crank twice as much data.

DDR3 modules achieve this high level of performance while using up even less power than DDR2 modules. This is a very desirable feature in mobile platforms like laptops or netbooks where energy is always in short supply. DDR3 modules also have slightly better latencies compared to DDR2 even though they are expected to have the same latency. This slight advantage is due to better manufacturing processes rather than by the DDR3 standard itself.

Though DDR3 has been around for some time, it has not fully replaced DDR2 as the mainstream memory. A contributing factor to this is the lack of backwards compatibility. DDR3 modules will not fit into a DDR2 slot even if it has the same number of pins. It is notched differently to prevent accidental insertion because their electrical characteristics are different; forcing them together would result to damage. Upgrading to DDR3 would certainly mean replacing you motherboard and probably even your processor which could cost a lot of money. Not to mention that the DDR3 module also costs more than DDR2 modules. Even if there are some barriers to the full adaptation of DDR3, it is already used in some devices like video cards which greatly benefits from the greater bandwidth.

The future of DDR3 is still quite unclear. Whether it will still be able to replace DDR2 or just get superseded by another standard is still under debate. This becomes even more of an issue as DDR4 is already under development.

1. The DDR2 memory clock runs at half of the system clock while the clock of DDR3 runs at quarter speed of the system clock
2. DDR3 has a higher maximum bandwidth compared to DDR2
3. DDR3 consumes less power than DDR2
4. DDR3 modules have slightly lower latencies than DDR2
5. DDR3 is not backwards compatible to DDR2
6. DDR3 costs more than DDR2

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  1. My Laptop’s RAM is 2GB DDR3. Using a hardware information software (PC Wizard) I got the following information-
    DDR3-SDRAM PC3-10700 (667MHz) – [DDR3-1333]
    As per my understanding it’s BUS speed is 1333MHz and data transfer rate is 10700MB/s. So, what is the significance of 667MHz?

    My Desktop’s RAM is 1GB DDR2.
    DDR2-SDRAM PC2-6400 (399MHz) – [DDR2-800]
    Here BUS speed 800MHz and data transfer rate is 6400MB/s. Same question here for 399MHz.

  2. I almost forgot. Laptop memory is 200 pins. Desktop memory is 240 pins. They’re shaped differently from each other and not interchangeable. So make sure you get the correct memory, if you take the splurge.

    Advice around the internet: DDR2 is no longer being manufactured so the price is rising. But there are tons of used DDR2 memory waiting for good homes. eBay looks to be a good outlet for this used market. As usual, you want a vendor with high customer ratings. It would also help if they’re aware of practicing static-electricity safety procedures.

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