RAM (Random Access Memory)
Random Access Memory (RAM) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device’s processor. RAM is the main memory in a computer, and it is much faster to read from and write to than other kinds of storage, such as a hard disk drive (HDD), solid-state drive (SSD) or optical drive.
DDR3
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 DDRand 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.
DDR3 is a DRAM interface specification. The actual DRAM arrays that store the data are similar to earlier types, with similar performance.
4 GiB PC3-12800 ECC DDR3 DIMM
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| Type | Synchronous dynamic random-access memory (SDRAM) |
|---|---|
| Release date | 2007 |
| Predecessor | DDR2 SDRAM (2003) |
| Successor | DDR4 SDRAM (2014) |
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 DDRand 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.
DDR3 is a DRAM interface specification. The actual DRAM arrays that store the data are similar to earlier types, with similar performance.
The primary benefit of DDR3 SDRAM over its immediate predecessor, DDR2 SDRAM, is its ability to transfer data at twice the rate (eight times the speed of its internal memory arrays), enabling higher bandwidth or peak data rates. With two transfers per cycle of a quadrupled clock signal, a 64-bit wide DDR3 module may achieve a transfer rate (in megabytes per second, MB/s) of up to 64 times the memory clock speed (in MHz). With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.
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 specification for 16 GiB DDR3 DIMMs.
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. DDR3 SO-DIMMs have 204 pins.
DDR3L and DDR3U extensions
The DDR3L (DDR3 Low Voltage) standard is an addendum to the JESD79-3 DDR3 Memory Device Standard specifying low voltage devices. The DDR3L standard is 1.35 V and has the label PC3L for its modules. Examples include DDR3L‐800 (PC3L-6400), DDR3L‐1066 (PC3L-8500), DDR3L‐1333 (PC3L-10600), and DDR3L‐1600 (PC3L-12800). The DDR3L and DDR3U specifications are compatible with the original DDR3 standard and can run at either the lower voltage or at 1.50 V.
Devices that require DDR3L, which operate at 1.35 V, such as systems using fourth-generation Intel Core processors, are not compatible with DDR3 operating at 1.50 V.
The DDR3U (DDR3 Ultra Low Voltage) standard is 1.25 V and has the label PC3U for its modules.
JEDEC Solid State Technology Association announced the publication of JEDEC DDR3L on July 26, 2010.
