All ranks are connected to the same memory bus (address + data). The term sides would also be confusing because it incorrectly suggests the physical placement of chips on the module. A memory module may bear more than one rank. The term was introduced to avoid confusion with chip internal rows and banks. Multiple chips with the common address lines are called a memory rank. For instance, the 64-bit data bus for DIMM requires eight 8-bit chips, addressed in parallel. To increase memory capacity and bandwidth, chips are combined on a module. Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.Ĭomparison of memory modules for portable/mobile PCs ( SO-DIMM).
Pc3 12800e ddr3 64 bits#
With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate (in bytes/s) of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a SDR SDRAM running at the same clock frequency, due to this double pumping. One advantage of keeping the clock frequency down is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to double data bus bandwidth without a corresponding increase in clock frequency. Implementations often have to use schemes such as phase-locked loops and self-calibration to reach the required timing accuracy. None of its successors are forward or backward compatible with DDR1 SDRAM, meaning DDR2, DDR3, DDR4 and DDR5 memory modules will not work in DDR1-equipped motherboards, and vice versa.Ĭompared to single data rate ( SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. DDR SDRAM, also retroactively called DDR1 SDRAM, has been superseded by DDR2 SDRAM, DDR3 SDRAM, DDR4 SDRAM and DDR5 SDRAM. Double Data Rate Synchronous Dynamic Random-Access Memory ( DDR SDRAM) is a double data rate (DDR) synchronous dynamic random-access memory (SDRAM) class of memory integrated circuits used in computers.
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