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The main differences between DDR1 (Double Data Rate) and DDR2 lie in the higher clocking and lower supply voltage of DDR2, which leads to a significantly improved memory bandwidth and power consumption.

Since power consumption decreases as the square of the supply voltage, this means that heat generation has been almost halved for the DDR2 device with 1.8 V voltage compared to the DDR1 device with 2.5 V. To improve signal integrity, DDR2 has an on-die termination that provides low- reflection signal matching even at high frequencies.

DDR2 is a memory standard adopted by the Joint Electron Device Engineering Council( JEDEC), defined for clock frequencies of 400 MHz, 533 MHz, 667 MHz and 800 MHz. It should be noted that the clock frequencies mentioned are already the clock frequency of the Front Side Bus( FSB) doubled by the DDR process. In accordance with the different clock rates, DDR2 has the variants DDR2-400 as PC2-3200 memory block, DDR2-533 as PC2-4200, DDR2-667 as PC2-5300 and DDR2-800 as PC/2-6400. DDR2-800 memory chips achieve data transfer rates of 6.4 GB/s.

DDR2 memory chips

DDR2 memory chips

DDR2 memory chips are designed in ball grid arrays( BGA) and soldered onto the memory latches using SMT technology. The memory bandwidth of a DDR2 memory chip is 3.2 GB/s with a memory bus width of 64 bits, for example with the PC2-3200. DDR2 is scalable and is also offered as DDR2-800.

Englisch: DDR2
Updated at: 19.03.2008
#Words: 231
Links: DDR1, clocking, voltage, memory, bandwidth (BW)
Translations: DE

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