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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 .
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.
In particular, each successive generation of DDR memory has higher transfer rates but the absolute latency does not change significantly, and especially when first appearing on the market, the new generation generally has longer latency than the previous one. The architecture and bugs in the CPUs can also change the latency.
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.
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 ]
DDR4 reached mass market adoption around 2015, which is comparable with the approximately five years taken for DDR3 to achieve mass market transition over DDR2. The DDR4 chips run at 1.2 V or less, [18] [19] compared to the 1.5 V of DDR3 chips, and have in excess of 2 billion data transfers per second.
JEDEC has set standards for the data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. The first retail PC motherboard using DDR SDRAM was released in August 2000. [10]
Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor.Memory bandwidth is usually expressed in units of bytes/second, though this can vary for systems with natural data sizes that are not a multiple of the commonly used 8-bit bytes.