DDR and DDR2: Know the Difference


Double Data Rate Random Access Memory (DDR RAM) and DDR2 RAM are both types of Synchronous Dynamic Random Access Memory (SDRAM). Both have a chipset support of basically all DTs, NBs, and servers. The key difference is that DDR2 is a second generation of DDR and has improved features compared to the latter. DDR was first released in 2000 with a voltage of 2.5 Volts. DDR’s speeds are 200 MHz, 266 MHz, 333 MHz, and 400 MHz and read latencies of 2, 2.5, and 3 clock cycles. Moreover, it has a write latency of 1 clock cycle. It has 4 internal banks and a Prefetch buffer of 2 bits. Also, its data strobe is single-ended with modules 184-pin DIMM unbuffered registered, 200-pin SODIMM, and 172-pin MicroDIMM.

Alternatively, DDR2 was first released in 2003 as a successor of DDR. It has 1.8 volts which is smaller than that of DDR. DDR2’s speeds are 400 MHz, 533 MHz, 667 MHz, 800 MHz, and 1066MT/s with read latencies of 3 – 9 clock cycles but may really depend on individual settings. Its write latency is equivalent to read latency minus 1 clock cycle. It has 4 or 8 internal banks and a Prefecth buffer of 4 bits. Lastly, it has either single-data or differential strobe and modules 40-pin DIMM, unbuffered registered, 200-pin SODIMM, and 214-pin MicroDIMM.



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