Comparison and Difference between DDR2 and DDR3 memory
Difference and Comparison between DDR2 and DDR3 memory
Most of the recent notebooks and computers of both AMD and Intel are coming up equipped with DDR2 and DDR3 memories. This FAQ should help you understand the difference in the DDR2 and DDR3 memories.
Q. Can I insert a DDR3 memory module in a motherboard designed for DDR2 memory ?
A. No, you can not insert DDR3 memory module in a motherboard designed for the DDR2 memory. They have different sockets and the pin outs.
Q. What are different speed grades of the DDR2 versus DDR3 memory available.
A. The DDR2 memory is available officially available in the speed range of 400 to 800 Megabits per second. The DDR3 memory is officially available in the speed range of 800 to 1600 Megabits per second. Speeds higher than 800 Mbps in DDR and higher than 1600 in DDR3 are also available, but they are not officially supported.
Q. How much is the real improvement in the memory throughput in DDR3 over DDR2
A. This is very good question. The actual throughput measurement involves the motherboard, CPU among other things and it makes the comparison difficult. However, there has not been any significant improvement in the performance between DDR2 and DDR3 even with the marked increase in the frequency. It is only after DDR3-1333 that you start to see something real in terms of the improvement in the throughput. Various benchmarks have reported 5% to 1% improvements depending upon the memory configuration and the speed grades of the memory you are comparing.
Q. I heard that the Cache Latency of DDR3 memory is higher than that of the DDR2. And that this makes DDR3 memory slower than the DDR2 memory.
A. You are correct in that the Cache Latency of the DDR3 memory is higher than the DDR2 memory. Cache Latency is defined at the time between the issue of the read command from the processor and the time when the data from the memory actually becomes available. It is measures in the units of clock cycles. A higher cache latency in DDR3 means that it becomes slower. However, cache latency is not the only thing determining the overall performance and speed of the DDR3 memory. The higher speed of the DDR3 memory more than makes up the issue of the cache latency.
Q. How about power consumptions ? Which of these two memories consume lower power ?
A. DDR3 memory was designed with power consumption in mind. DDR3 consumes substantially lower power than the DDR2 memory. This especially helps the notebooks that are supposed to work on batteries and the battery life is a concern.
Q. What technological challenge is presented in the architecture and design of the DDR3 memory.
A. Since DDR3 memory works much faster than the DDR2 memory, there are Signal Integrity challenges to keep the memory part running at much higher frequency. Also the DDR3 memory has been designed to work at lower voltage level. Lower voltage means that a small amount of noise in the power supply rail can lead to error and failure. This is manifested in terms of system hanging. The designers using DDR3 must analyze the platform and the system motherboard to ensure that it stays robust under all conditions of temperature and voltage variations.
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