Search results
Results from the WOW.Com Content Network
DDR SDRAM specification was finalized by JEDEC in June 2000 (JESD79). [9] JEDEC has set standards for the data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. The first retail PC motherboard using DDR SDRAM was released in August 2000. [10]
Some other computer architectures use different modules with a different bus width. In a single-channel configuration, only one module at a time can transfer information to the CPU. In multi-channel configurations, multiple modules can transfer information to the CPU at the same time, in parallel.
DDR SDRAM operating with a 100 MHz clock is called DDR-200 (after its 200 MT/s data transfer rate), and a 64-bit (8-byte) wide DIMM operated at that data rate is called PC-1600, after its 1600 MB/s peak (theoretical) bandwidth. Likewise, 12.8 GB/s transfer rate DDR3-1600 is called PC3-12800. Some examples of popular designations of DDR modules:
The naming convention for DDR, DDR2 and DDR3 modules specifies either a maximum speed (e.g., DDR2-800) or a maximum bandwidth (e.g., PC2-6400). The speed rating (800) is not the maximum clock speed, but twice that (because of the doubled data rate). The specified bandwidth (6400) is the maximum megabytes transferred per second using a 64-bit width.
DDR SDRAM (sometimes called DDR1 for greater clarity) doubles the minimum read or write unit; every access refers to at least two consecutive words. Typical DDR SDRAM clock rates are 133, 166 and 200 MHz (7.5, 6, and 5 ns/cycle), generally described as DDR-266, DDR-333 and DDR-400 (3.75, 3, and 2.5 ns per beat).
DDR4 speeds are advertised as double the base clock rate due to its Double Data Rate (DDR) nature, with common speeds including DDR4-2400 and DDR4-3200, and higher speeds like DDR4-4266 and DDR4-5000 available at a premium. Unlike DDR3, DDR4 does not have a low voltage variant; it consistently operates at 1.2 V. Additionally, DDR4 improves on ...
Double data rate SDRAM (DDR SDRAM or DDR) was a later development of SDRAM, used in PC memory beginning in 2000. Subsequent versions are numbered sequentially (DDR2, DDR3, etc.). DDR SDRAM internally performs double-width accesses at the clock rate, and uses a double data rate interface to transfer one half on each clock edge. DDR2 and DDR3 ...
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. 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. This is twice DDR2's data transfer rates (400 ...