SDRAM and its significance

SDRAM stands for Synchronous dynamic random access memory. SDRAM devices are synchronised to system bus and it waits to sync with system bus before responding to the input controls. This enables SDRAM to function at higher speeds than DRAM. SDRAM cards are widely used in computers.

DDR, DDR2 and DDR3 are generations of memory modules than have been developed from SDRAM. SDRAM has auto refresh feature which allows refresh the data without physically removing the device from the computer. SDRAM also has a low power mode. SDRAM is relatively a slower version than DDR as the SDRAM chip only transmits single word of data per clock cycle.

The initial SDRAM was also called Single Data Rate SDRAM also known as SDR SDRAM. A double data interface was developed for SDRAM modules which enable to transfer two data words in a single clock cycle so that the device can perform with high speed transfers. This was named as DDR SDRAM.

DDR Memory

DDR, the short form of Double Data Rate is one kind of memory module that transfers data at a doubling rate than a SDRAM memory module. It means it transfers two data portion per clock sequence. In order to get the maximum performance, this memory needs to be used in a moderately updated computer system.

However, if a memory module is labeled with DDR-800, then it is capable of working at 400MHz speed. The label indicates the maximum range that this memory module can support. Since, the controller used for this kind of memory is located outside the module and somewhere within the CPU, so the data transfer rate may vary accordingly.