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Increasing memory bandwidth, even while increasing memory latency, may improve the performance of a computer system with multiple processors and/or multiple execution threads. Higher bandwidth will also boost performance of integrated graphics processors that have no dedicated video memory but use regular RAM as VRAM.
Memory latency is the time (the latency) between initiating a request for a byte or word in memory until it is retrieved by a processor. If the data are not in the processor's cache, it takes longer to obtain them, as the processor will have to communicate with the external memory cells. Latency is therefore a fundamental measure of the speed ...
Some other computer architectures use different modules with a different bus width. In a single-channel configuration, only one module at a time can transfer information to the CPU. In multi-channel configurations, multiple modules can transfer information to the CPU at the same time, in parallel.
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 .
Column address strobe latency, also called CAS latency or CL, is the delay in clock cycles between the READ command and the moment data is available. [ 1 ] [ 2 ] In asynchronous DRAM , the interval is specified in nanoseconds (absolute time). [ 3 ]
Double data rate SDRAM (DDR SDRAM or DDR) was a later development of SDRAM, used in PC memory beginning in 2000. Subsequent versions are numbered sequentially ( DDR2 , DDR3 , etc.). DDR SDRAM internally performs double-width accesses at the clock rate, and uses a double data rate interface to transfer one half on each clock edge.
DDR3 and DDR4 use A12 during read and write command to indicate "burst chop", half-length data transfer; DDR4 changes the encoding of the activate command. A new signal ACT controls it, during which the other control lines are used as row address bits 16, 15 and 14. When ACT is high, other commands are the same as above.
In computing, serial presence detect (SPD) is a standardized way to automatically access information about a memory module.Earlier 72-pin SIMMs included five pins that provided five bits of parallel presence detect (PPD) data, but the 168-pin DIMM standard changed to a serial presence detect to encode more information.