Overview
Compared to DDR2 memory, DDR3 memory uses 30% less power. This reduction comes from the difference in supply voltages: 1.8V or 2.5V for DDR2, and 1.5V for DDR3. 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.
According to JEDEC, 1.575 volts 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 its prefetch buffer, which is 8-burst-deep. In contrast, the prefetch buffer of DDR2 is 4-burst-deep, and the prefetch buffer of DDR is 2-burst-deep.
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 does use the same electric signaling standard as DDR and DDR2, Stub Series Terminated Logic, albeit at different timings and voltages. Specifically, DDR3 uses SSTL_15.
DDR3 prototypes were announced in early 2005. Products in the form of motherboards appeared on the market in June 2007 based on Intel's P35 "Bearlake" chipset with DIMMs at bandwidths up to DDR3-1600 (PC3-12800). 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 first socket AM3 Phenom II X4 processors, released in February 2009, were their first to support DDR3.
DDR3 DIMMs have 240 pins and are electrically incompatible with DDR2. The two are prevented from being accidentally interchanged by different key notch positions on the DIMMs. DDR3 SO-DIMMs have 204 pins.
GDDR3 memory, sometimes incorrectly referred to as "DDR3" due to its similar name, is an entirely different technology, as it is designed for use in graphics cards and is based on DDR2 SDRAM.
Read more about this topic: DDR3 SDRAM