Answer Description
DDR RAM (Double Data Rate - Random Access Memory) was designed to use two parallel channels to communicate with a motherboard's memory controller. DRAM and SDRAM use a single channel to communicate with the memory controller. While Flash Memory is capable of using multiple channels, it is non-volatile as it retains data without constant power.
Wikipedia
In computing, a computer bus operating with double data rate (DDR) transfers data on both the rising and falling edges of the clock signal This is also known as double pumped, dual-pumped, and double transition The term toggle mode is used in the context of NAND flash memory The simplest way to design a clocked electronic circuit is to make it perform one transfer per full cycle (rise and fall) of a clock signal This, however, requires that the clock signal changes twice per transfer, while the data lines change at most once per transfer When operating at a high bandwidth, signal integrity limitations constrain the clock frequency
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