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ddr3 [2016/05/30 18:37]
gongyu 创建 		ddr3 [2016/05/30 18:46]
gongyu
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 Double data rate type three SDRAM (DDR3 SDRAM) is a type of synchronous dynamic random-access memory (SDRAM) with a high bandwidth ("​double data rate") interface, and has been in use since 2007. It is the higher-speed successor to DDR and DDR2 and predecessor to DDR4 synchronous dynamic random-access memory (SDRAM) chips. DDR3 SDRAM is neither forward nor backward compatible with any earlier type of random-access memory (RAM) because of different signaling voltages, timings, and other factors. Double data rate type three SDRAM (DDR3 SDRAM) is a type of synchronous dynamic random-access memory (SDRAM) with a high bandwidth ("​double data rate") interface, and has been in use since 2007. It is the higher-speed successor to DDR and DDR2 and predecessor to DDR4 synchronous dynamic random-access memory (SDRAM) chips. DDR3 SDRAM is neither forward nor backward compatible with any earlier type of random-access memory (RAM) because of different signaling voltages, timings, and other factors.
 +{{ :​4gb_ddr3_so-dimm.jpg |400}}
 DDR3 is a DRAM interface specification. The actual DRAM arrays that store the data are similar to earlier types, with similar performance. DDR3 is a DRAM interface specification. The actual DRAM arrays that store the data are similar to earlier types, with similar performance.
  
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 The DDR3 standard permits DRAM chip capacities of up to 8 gibibits, and up to 4 ranks of 64 bits each for a total maximum of 16 GiB per DDR3 DIMM. Because of a hardware limitation not fixed until Ivy Bridge-E in 2013, most older Intel CPUs only support up to 4 gibibit chips for 8 GiB DIMMs (Intel'​s Core 2 DDR3 chipsets only support up to 2 gibibits). All AMD CPUs correctly support the full spec for 16GiB DDR3 DIMMs. The DDR3 standard permits DRAM chip capacities of up to 8 gibibits, and up to 4 ranks of 64 bits each for a total maximum of 16 GiB per DDR3 DIMM. Because of a hardware limitation not fixed until Ivy Bridge-E in 2013, most older Intel CPUs only support up to 4 gibibit chips for 8 GiB DIMMs (Intel'​s Core 2 DDR3 chipsets only support up to 2 gibibits). All AMD CPUs correctly support the full spec for 16GiB DDR3 DIMMs.
  
-Overview[edit] +====Overview====
-Physical comparison of DDR, DDR2, and DDR3 SDRAM+
 Three long green circuit boards, identical in size, but each with a notch in a different location Three long green circuit boards, identical in size, but each with a notch in a different location
-Desktop PCs (DIMM)+ 
 +{{ :​573px-desktop_ddr_memory_comparison.svg.png |}} 
 +<WRAP centeralign>​ **Desktop PCs (DIMM)** </​WRAP>​
 Three short green circuit boards, identical in size, but each with a notch in a different location Three short green circuit boards, identical in size, but each with a notch in a different location
-Notebook and convertible PCs (SO-DIMM) 
-Compared to DDR2 memory, DDR3 memory uses less power. This reduction comes from the difference in supply voltages: 1.8 V or 1.9 V for DDR2 versus 1.35 V or 1.5 V for DDR3. The 1.5 V supply voltage works well with the 90 nanometer fabrication technology used in the original DDR3 chips.[citation needed] Some manufacturers further propose using "​dual-gate"​ transistors to reduce leakage of current.[2] 
  
-According to JEDEC,​[3]:​111 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 1.80 volts[a] before incurring permanent damage, although they are not required to function correctly at that level.[3]:109+{{ :​400px-laptop_sodimm_ddr_memory_comparison_v2.svg.png |}} 
 +<WRAP centeralign>​ **Notebook and convertible PCs (SO-DIMM)**</​WRAP>​ 
 + 
 +Compared to DDR2 memory, DDR3 memory uses less power. This reduction comes from the difference in supply voltages: 1.8 V or 1.9 V for DDR2 versus 1.35 V or 1.5 V for DDR3. The 1.5 V supply voltage works well with the 90 nanometer fabrication technology used in the original DDR3 chips.[citation needed] Some manufacturers further propose using "​dual-gate"​ transistors to reduce leakage of current. 
 + 
 +According to JEDEC,​[3]:​111 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 1.80 volts[a] before incurring permanent damage, although they are not required to function correctly at that level.
  
 Another benefit is 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. This advantage is an enabling technology in DDR3's transfer speed. Another benefit is 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. This advantage is an enabling technology in DDR3's transfer speed.
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 Because the hertz is a measure of cycles per second, and no signal cycles more often than every other transfer, describing the transfer rate in units of MHz is technically incorrect, although very common. It is also misleading because various memory timings are given in units of clock cycles, which are half the speed of data transfers. Because the hertz is a measure of cycles per second, and no signal cycles more often than every other transfer, describing the transfer rate in units of MHz is technically incorrect, although very common. It is also misleading because various memory timings are given in units of clock cycles, which are half the speed of data transfers.
  
-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.[5]+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[6] based on Intel'​s P35 "​Bearlake"​ chipset with DIMMs at bandwidths up to DDR3-1600 (PC3-12800).[7] 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 prototypes were announced in early 2005. Products in the form of motherboards appeared on the market in June 2007[6] based on Intel'​s P35 "​Bearlake"​ chipset with DIMMs at bandwidths up to DDR3-1600 (PC3-12800).[7] 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.
  
-Dual-inline memory modules[edit]+====Dual-inline memory modules====
 DDR3 dual-inline memory modules (DIMMs) have 240 pins and are electrically incompatible with DDR2. A key notch—located differently in DDR2 and DDR3 DIMMs—prevents accidentally interchanging them. Not only are they keyed differently,​ but DDR2 has rounded notches on the side and the DDR3 modules have square notches on the side. [8] DDR3 SO-DIMMs have 204 pins.[9] DDR3 dual-inline memory modules (DIMMs) have 240 pins and are electrically incompatible with DDR2. A key notch—located differently in DDR2 and DDR3 DIMMs—prevents accidentally interchanging them. Not only are they keyed differently,​ but DDR2 has rounded notches on the side and the DDR3 modules have square notches on the side. [8] DDR3 SO-DIMMs have 204 pins.[9]