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DDR SDRAM is computer memory that operates at nearly double the speed of SDRAM. It transfers data using double pumping and comes in modules with 184 pins. The transfer rate is calculated by multiplying the memory clock rate by two and then by 64, divided by eight to get MB/s. JEDEC sets manufacturing standards for memory rates and package sizes. DDR and SD models can be distinguished by the number of notches on the memory card. When purchasing computer memory, examine the motherboard to determine what type of memory is needed.
Double data rate synchronous dynamic random access memory, or DDR SDRAM, is computer memory. The older version is single data rate or SDRAM. DDR SDRAM was built on the technology of the previous version, but operates at nearly double the bandwidth or processing speed.
This is possible because the data is transferred using the double pumping technique. In this technique, data is transferred as the clock goes up and down. An added benefit of this process is that no changes or adjustments to the clock frequency are required.
DDR memory transfers data in 64-bit chunks. Actual transfer speed is calculated by multiplying the memory clock rate by two, since this is twice the unit. This value is then multiplied by 64, which is the number of bits that have been transferred. The total value is divided by eight, which is a unit conversion for bits for bytes. The final value is given in megabytes per second or MB/s.
There are manufacturing standard data rates for memory, established by the Joint Electron Device Engineering Council (JEDEC). This standard is divided into memory chips and memory modules. Even the standard naming convention is divided into two categories: industry and consumer. The sector name is DDR, followed by the number of data transfers per second. For example, a DDR-200 component provides a data transfer rate of 200 bits per second.
The consumer naming convention is based on the peak transfer rate. DDR-200 has a maximum transfer speed of 1,600. Therefore, this unit would be called PC – 1600 in the consumer market. It is exactly the same as the DDR-200 drive. Package sizes are also set by the JEDEC, in the interest of consistency between manufacturers.
A DDR SDRAM module has 184 pins for desktop computer dual inline memory modules (DIMMs). SD RAM has 168 pins, and DDR2 SDRAM, which is the later version of DDR SDRAM, has 240. It’s easy to tell the DDR and SD models apart, just by looking at the number of notches on the memory card. The DDR version has one and the SD version has two.
When purchasing computer memory, you should examine your computer’s motherboard to determine what type of memory you need. Remove the plastic case from the computer by unscrewing the screws on the sides and lifting the cover. Memory cards are 3 inches (7.6 cm) long and have a series of black circuits connected to a green card. They are attached to the motherboard via a long black plug-in module. To remove a memory card, unlock the side clips and take out the memory.
