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Usually several memory cells share the same address. For example, a 4 bit "wide" RAM chip has four memory cells for each address. Often the width of the memory and that of the microprocessor are different, for a 32 bit microprocessor, eight 4 bit RAM chips would be needed. Often more addresses are needed than can be provided by a device.
DDR2 and DDR3 increased this factor to 4× and 8×, respectively, delivering 4-word and 8-word bursts over 2 and 4 clock cycles, respectively. The internal access rate is mostly unchanged (200 million per second for DDR-400, DDR2-800 and DDR3-1600 memory), but each access transfers more data.
The DDR4 SDRAM is a high-speed dynamic random-access memory internally configured as 16 banks, 4 bank groups with 4 banks for each bank group for ×4/×8 and 8 banks, 2 bank groups with 4 banks for each bank group for ×16 DRAM. The DDR4 SDRAM uses an 8n prefetch architecture to achieve high-speed operation.
DDR4 RAM operates at a voltage of 1.2 V and supports frequencies between 800 and 1600 MHz (DDR4-1600 through DDR4-3200). Compared to DDR3, which operates at 1.5 V with frequencies from 400 to 1067 MHz (DDR3-800 through DDR3-2133), DDR4 offers better performance and energy efficiency. DDR4 speeds are advertised as double the base clock rate due ...
Dual-ported RAM (DPRAM), also called dual-port RAM, is a type of random-access memory (RAM) that can be accessed via two different buses.. A simple dual-port RAM may allow only read access through one of the ports and write access through the other, in which case the same memory location cannot be accessed simultaneously through the ports since a write operation modifies the data and therefore ...
There is only a little difference between a dual rank UDIMM and two single-rank UDIMMs in the same memory channel, other than that the DRAMs reside on different PCBs. The electrical connections between the memory controller and the DRAMs are almost identical (with the possible exception of which chip selects go to which ranks). Increasing the ...
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The key difference between DDR2 and DDR SDRAM is the increase in prefetch length. In DDR SDRAM, the prefetch length was two bits for every bit in a word; whereas it is four bits in DDR2 SDRAM. During an access, four bits were read or written to or from a four-bit-deep prefetch queue.