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`What is the difference between SDRAM, DDR1, DDR2, DDR3 and DDR4? - Transcend Information, Inc.
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`What is the difference between SDRAM, DDR1, DDR2, DDR3 and
`DDR4?
`
`Category : Specification / Capacity / Performance
`
`SDRAM (Synchronous Dynamic Random Access Memory):
`"Synchronous" tells about the behaviour of the DRAM type. In late 1996, SDRAM began to appear in systems. Unlike previous
`technologies, SDRAM is designed to synchronize itself with the timing of the CPU. This enables the memory controller to know the
`exact clock cycle when the requested data will be ready, so the CPU no longer has to wait between memory accesses. For example,
`PC66 SDRAM runs at 66 MT/s, PC100 SDRAM runs at 100 MT/s, PC133 SDRAM runs at 133 MT/s, and so on.
`SDRAM can stand for SDR SDRAM (Single Data Rate SDRAM), where the I/O, internal clock and bus clock are the same. For example,
`the I/O, internal clock and bus clock of PC133 are all 133 Mhz. Single Data Rate means that SDR SDRAM can only read/write one time
`in a clock cycle. SDRAM have to wait for the completion of the previous command to be able to do another read/write operation.
`
`DDR SDRAM (Double Data Rate SDRAM):
`The next generation of SDRAM is DDR, which achieves greater bandwidth than the preceding single data rate SDRAM by transferring
`data on the rising and falling edges of the clock signal (double pumped). Effectively, it doubles the transfer rate without increasing the
`frequency of the clock. The transfer rate of DDR SDRAM is the double of SDR SDRAM without changing the internal clock. DDR SDRAM,
`as the first generation of DDR memory, the prefetch buffer is 2bit, which is the double of SDR SDRAM. The transfer rate of DDR is
`between 266~400 MT/s. DDR266 and DDR400 are of this type.
`
`DDR2 SDRAM(Double Data Rate Two SDRAM):
`Its primary benefit is the ability to operate the external data bus twice as fast as DDR SDRAM. This is achieved by improved bus signal.
`The prefetch buffer of DDR2 is 4 bit(double of DDR SDRAM). DDR2 memory is at the same internal clock speed (133~200MHz) as DDR,
`but the transfer rate of DDR2 can reach 533~800 MT/s with the improved I/O bus signal. DDR2 533 and DDR2 800 memory types are
`on the market.
`
`DDR3 SDRAM(Double Data Rate Three SDRAM):
`DDR3 memory reduces 40% power consumption compared to current DDR2 modules, allowing for lower operating currents and
`voltages (1.5 V, compared to DDR2's 1.8 V or DDR's 2.5 V). The transfer rate of DDR3 is 800~1600 MT/s. DDR3's prefetch buffer width is
`8 bit, whereas DDR2's is 4 bit, and DDR's is 2 bit. DDR3 also adds two functions, such as ASR (Automatic Self-Refresh) and SRT (Self-
`Refresh Temperature). They can make the memory control the refresh rate according to the temperature variation.
`
`DDR4 SDRAM (Double Data Rate Fourth SDRAM):
`DDR4 SDRAM provides the lower operating voltage (1.2V) and higher transfer rate. The transfer rate of DDR4 is 2133~3200 MT/s.
`DDR4 adds four new Bank Groups technology. Each bank group has the feature of singlehanded operation. DDR4 can process 4 data
`within a clock cycle, so DDR4's efficiency is better than DDR3 obviously. DDR4 also adds some functions, such as DBI
`(Data Bus Inversion), CRC (Cyclic Redundancy Check) and CA parity. They can enhance DDR4 memory's signal integrity, and improve
`the stability of data transmission/access.
`
`https://www.transcend-info.com/support/faq-296#:~:text=DDR3's prefetch buffer width is,according to the temperature variation.
`
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`Netlist Ex 2018
`Samsung v Netlist
`IPR2022-00996
`
`
`
`8/24/22, 11:59 AM
`
`What is the difference between SDRAM, DDR1, DDR2, DDR3 and DDR4? - Transcend Information, Inc.
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`(/Support/FAQ/FAQPics/DDR.JPG)
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`https://www.transcend-info.com/support/faq-296#:~:text=DDR3's prefetch buffer width is,according to the temperature variation.
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