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DDR2 DIMMs are neither forward compatible with DDR3 nor backward compatible with DDR. In addition to double pumping the data bus as in DDR SDRAM (transferring data on the rising and falling edges of the bus clock signal), DDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus. The ...
DDR2 DDR3: Regor 2 1600–3600 2000 HT 512, 1024 DDR2 DDR3: Sempron: Sargas 130 1 2600 2000 HT 512 DDR2 DDR3: MMX, SSE, SSE2, SSE3, SSE4a, Enhanced 3DNow! PowerNow! AMD64, NX bit, AMD-V: 140 2700 1024 145 2800 150 2900 Turion II: Caspian 2 2000–2700 1800, 1600 HT 512, 1024 Socket S1G3 DDR2: 32 Llano: Llano
The naming convention for DDR, DDR2 and DDR3 modules specifies either a maximum speed (e.g., DDR2-800) or a maximum bandwidth (e.g., PC2-6400). The speed rating (800) is not the maximum clock speed, but twice that (because of the doubled data rate). The specified bandwidth (6400) is the maximum megabytes transferred per second using a 64-bit width.
DDR and DDR2 memory is usually installed in single- or dual-channel configuration. DDR3 memory is installed in single-, dual-, tri-, and quad-channel configurations. Bit rates of multi-channel configurations are the product of the module bit-rate (given below) and the number of channels.
Corresponding 240-pin DIMMs are known as PC2-3200 through PC2-6400. DDR2 SDRAM is now available at a clock rate of 533 MHz generally described as DDR2-1066 and the corresponding DIMMs are known as PC2-8500 (also named PC2-8600 depending on the manufacturer). Performance up to DDR2-1250 (PC2-10000) is available.
What determines absolute latency (and thus system performance) is determined by both the timings and the memory clock frequency. When translating memory timings into actual latency, timings are in units of clock cycles, which for double data rate memory is half the speed of the commonly quoted transfer rate. Without knowing the clock frequency ...
DDR2 started to be effective by the end of 2004, as modules with lower latencies became available. [ 19 ] Memory manufacturers stated that it was impractical to mass produce DDR1 memory with effective transfer rates in excess of 400 MHz (i.e. 400 MT/s and 200 MHz external clock) due to internal speed limitations.
Memory controller with differential serial connections to DDR2 FB-DIMMs. The AMB is visible in the center of each DIMM. A Fully Buffered DIMM (FB-DIMM) is a type of memory module used in computer systems. It is designed to improve memory performance and capacity by allowing multiple memory modules to be each connected to the memory controller ...