| • Science | • People | • Locations | • Timeline |
With data being transferred 8 bytes at a time DDR RAM gives a transfer rate of (memory bus clock rate) * 2 (for dual rate) * 8 (number of bytes transferred). Thus with a bus frequency of 100MHz, DDR RAM gives a transfer rate of 1600 MB/ s. This leads to each DDR RAM speed having two different names, one being its effective clock rate (e.g DDR200) and the other being its transfer rate (e.g PC1600).
The package sizes in which DDR SDRAM is manufactured are also standardised by JEDEC.
There is no architectural difference between DDR SDRAM designed for different clock frequencies, e.g DDR200 (designed to run at 100MHz) and DDR266 (designed to run at 133MHz). The number simply designates the speed that the chip is guaranteed to run at. Hence you can run DDR SDRAM at lower clock speeds then it was made for ( underclocking) or higher clock speeds then it was made for ( overclocking). Note that overclocking should only be done with high quality memory and by those that know what they are doing (see overclocking for details on why).
DDR SDRAM DIMMDIMM is an abbreviation for Dual In-line Memory Module and is a form of RAM for usage in personal computers. DIMMs began to replace SIMMs as the predominant type of memory module when Intel's Pentium processors were in the mainstream market. The most comms have 184 pins (as opposed to 168 on SDRAM), but are physically the same apart from the extra pins. DDR operates at a voltage of 2.5 VThe volt is the SI derived unit for electric potential and voltage (derived from the ampere and watt). It is named in honor of Alessandro Volta, who, in 1800, invented the voltaic pile, the first chemical battery. The volt is defined as the potential diff, compared to 3.3V for SDRAM. This can significantly reduce power usage.
Some new chipsets use these memory types in dual or even quad channel configurations, which doubles or quadruples the effective bandwidth. In the dual-channel configuration it is recommended to use a matched pair of memory modules to optimize performance. The modules in a pair have the same size, speed, and latency timings, enabling the chipset to interleave accesses with maximum efficiency.
DDR is slowly being replaced by DDR-IIDDR-II SDRAM (Double Data Rate Two Synchronous Dynamic Random Access Memory) is a computer memory technology that is expected to become a mainstream solution at some point late in 2004. The main advantage of DDR-II over DDR-I is its ability to work at hig, which has some modifications to allow higher clock frequency, but operates on the same principle as DDR. Competing with DDR-II will be RambusThe Company Rambus Incorporated, founded in 1990, is a provider of high-speed interface technology. Rambus is best known for their Rambus Direct RAM memory technology, which was intended to replace SDRAM as the standard memory used in computers. In 1996, XDR-DRAM . It is expected that DDR-II will become the standard, since QDR (Quad Data Rate) is too complex to implement, while XDR is lacking support.
Memory manufacturers have stated that it is impractical to mass-produce DDR-I memory with effective clock rates in excess of 400MHz. DDR-II picks up where DDR-I leaves off, and is available at clock rates of 400MHz and higher.
RDRAMRambus DRAM or RDRAM is a type of synchronous dynamic RAM, created by the Rambus Corporation. It has also been incorporated into the Sony PlayStation 2 and a line of Cray Supercomputers. Intel originally advocated the use of RDRAM in all Pentium 4 motherb is an alternative to DDR SDRAM, but most manufacturers have dropped support from their chipsets.