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DDR3 vs. DDR2. Is It Worth The Upgrade?

January 6th 2008File under: Hardware, MemoryIt is not long ago that we wrote a comparison between DDR2 and DDR RAM. Now, with the

launch of the new DDR3 technology, it is high time that we carry out another comparisonbetween DDR3 and DDR2 and decide if it really worth the upgrade from your existing system.

The difference between DDR2 and DDR3

On the appearance, both DDR3 and DDR2 use 240 pins and you can hardly see any differencesbetween them. The only difference is the position of the key notch that prevents users frominserting the wrong type of RAM into their motherboards. The shift in the position of the key

notch also means that DDR3 is not compatible with DDR2 and a separate DIMM slot has to beused.

Other than the difference in key notch position, DDR3 RAM is also due to run at a higherfrequency than DDR2 RAM. The specification provided by JEDEC provides more insight to itsperformance.

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Official JEDEC Specifications

DDR 2 DDR3

Transfer Speed 400 800 Mbps 800 1600 Mbps

Voltage 1.8V +/- 0.1V 1.5V +/- 0.075V

Internal Banks 4 8

Prefetch 4bits 8 bits

Termination Limited All DQ signals

Topology Conventional T Fly-by

CAS Latency 3 5 6 10

Thermal Sensor No Yes (optional)

When JEDEC set the standard for DDR2 RAM, it never intends to make it run beyond 800MHz.The official specification states that DDR speeds ran to DDR-400, DDR2 from 400 to 800, andDDR3 800 to 1600. Due to the fact that DDR2 800 and 1066 (an overclock version of DDR2800) exist, DDR3 800 and 1066 will become an overlap speed with that of DDR2. As such, itwill only be 1333 that is the first DDR3 speed to have better frequency/speed performance overthe DDR2 RAM.

While the difference between DDR and DDR2 RAM lies in the doubling of the frequency bus,the DDR3 works by doubling the prefetch data. This is achieved by doubling the internal bank to8. Each internal bank can process 1 bit of data. DDR2 SDRAM have only 4 internal banks andprocess 4-bit samples, DDR3 SDRAM uses 8 internal banks to carry out 8-bit prefetch. Theimpact of the additional internal banks means that the DDR3 SDRAM could double the datatransfer rate without having to make modifications to the original design.

Another advantage of DDR3 is the reduced voltage requirement. The required voltage for DDR3is 1.5V, a 16% reduction of the DDR2 1.8V. This could translate to a 30% reduction in powerconsumption compared with DDR2 RAM operating at the same speed. Additional built-in powerconservation features with DDR3 include partial refresh and thermal sensor that could allow thesystem to save further power by providing minimum refresh cycles when the system is not inhigh performance mode.

A point that requires attention and that brings DDR2 RAM back to the game is the price of theDDR3 RAM. A 1GB DDR3 1066MHz RAM is currently selling at over $200, which is double

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the price of a 1GB DDR2 1066MHz RAM. While there is no significant improvement of theDDR3-1066 RAM over DDR2-1066 RAM, there really isnt any compelling reason to upgradeyour current DDR2 RAM.

Conclusion

In the near future, it is inevitable that DDR3 is going to replace DDR2 as the standard formemory RAM. At this current moment, the hefty price hardly make it a must-upgradecomponent, considering that you can get a DDR2 RAM operating at the same speed for under$150. Until the time when higher speed DDR3 RAM are more readily available and the price fallto a reasonable range that is comparable to DDR2, it is better to remain with your DDR2 RAM.