Monday, August 16, 2010


DDR3 memory provides a reduction in power consumption of 30% compared to DDR2 modules due to DDR3's 1.5 V supply voltage, compared to DDR2's 1.8 V or DDR's 2.5 V. The 1.5 V supply voltage works well with the 90 nanometer fabrication technology used in the original DDR3 chips. Some manufacturers further propose using "dual-gate" transistors to reduce leakage of current.[1]

According to JEDEC[2] the maximum recommended voltage is 1.575 volts and should be considered the absolute maximum when memory stability is the foremost consideration, such as in servers or other mission critical devices. In addition, JEDEC states that memory modules must withstand up to 1.975 volts before incurring permanent damage, although they are not required to function correctly at that level.

The main benefit of DDR3 comes from the higher bandwidth made possible by DDR3's 8-burst-deep prefetch buffer, in contrast to DDR2's 4-burst-deep or DDR's 2-burst-deep prefetch buffer.

DDR3 modules can transfer data at a rate of 800–2133 MT/s using both rising and falling edges of a 400–1066 MHz I/O clock. Sometimes, a vendor may misleadingly advertise the I/O clock rate by labeling the MT/s as MHz. The MT/s is normally twice that of MHz by double sampling, one on the rising clock edge, and the other, on the falling. In comparison, DDR2's current range of data transfer rates is 400–1066 MT/s using a 200–533 MHz I/O clock, and DDR's range is 200–400 MT/s based on a 100–200 MHz I/O clock. High-performance graphics was an initial driver of such bandwidth requirements, where high bandwidth data transfer between framebuffers is required.

DDR3 prototypes were announced in early 2005. Products in the form of motherboards appeared on the market in June 2007[3] based on Intel's P35 "Bearlake" chipset with DIMMs at bandwidths up to DDR3-1600 (PC3-12800).[4] The Intel Core i7, released in November 2008, connects directly to memory rather than via a chipset. The Core i7 supports only DDR3. AMD's firstsocket AM3 Phenom II X4 processors, released in February 2009, were their first to support DDR3.

DDR3 DIMMs have 240 pins, are electrically incompatible with DDR2 and have a different key notch location.[5] DDR3 SO-DIMMs have 204 pins.[6]

GDDR3 memory, having a similar name but being from an entirely dissimilar technology, has been in use for graphic cards. GDDR3 has sometimes been incorrectly referred to as "DDR3".

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