19 Facts About SDRAM


SDRAM has a synchronous interface, whereby changes on control inputs are recognised after a rising edge of its clock input.

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SDRAM latency is not inherently lower than asynchronous DRAM.

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Indeed, early SDRAM was somewhat slower than contemporaneous burst EDO DRAM due to the additional logic.

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Today, virtually all SDRAM is manufactured in compliance with standards established by JEDEC, an electronics industry association that adopts open standards to facilitate interoperability of electronic components.

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Double data rate SDRAM, known as DDR SDRAM, was first demonstrated by Samsung in 1997.

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SDRAM is available in registered varieties, for systems that require greater scalability such as servers and workstations.

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Today, the world's largest manufacturers of SDRAM include: Samsung Electronics, SK Hynix, Micron Technology, and Nanya Technology.

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SDRAM devices are internally divided into either two, four or eight independent internal data banks.

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Later double-data-rate SDRAM standards add additional mode registers, addressed using the bank address pins.

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For example, DDR2 SDRAM has a 13-bit mode register, a 13-bit extended mode register No 1, and a 5-bit extended mode register No 2 .

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The SDRAM maintains an internal counter, which iterates over all possible rows.

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SDRAM designed for battery-powered devices offers some additional power-saving options.

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DDR SDRAM employs prefetch architecture to allow quick and easy access to multiple data words located on a common physical row in the memory.

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DDR2 SDRAM is very similar to DDR SDRAM, but doubles the minimum read or write unit again, to four consecutive words.

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Unlike SDRAM, there were no per-chip select signals; each chip was assigned an ID when reset, and the command contained the ID of the chip that should process it.

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VCM was a proprietary type of SDRAM that was designed by NEC, but released as an open standard with no licensing fees.

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Unlike a normal SDRAM write, which must be performed to an active row, the VCSDRAM bank must be precharged when the restore command is issued.

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Graphics double data rate SDRAM is a type of specialized DDR SDRAM designed to be used as the main memory of graphics processing units .

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GDDR SDRAM is distinct from commodity types of DDR SDRAM such as DDR3, although they share some core technologies.

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