SDRAM: Synchronous Dynamic Random Access Memory
Started to be used in systems in 1996 Unlike older variants it timed its processes to the CPU clock speed. This makes the system more efficient as the CPU does not have to wait for the memory to catch up to receive the information ready for processing. This type of memory is only Single Data Rate which means the I/O, internal clock and bus clock are the same. This has the negative of this type of Ram only being able to read/write once per CPU cycle. This means it will have to wait for the next cycle to give new information.
This stands for Double Data Rate SDRAM. This allows the transfer of data twice per clock cycle. This improves the rate at which tasks are performed as it does no limit the the rate the CPU and process the information. This doubles the speed at which data can be passed without changing the overall clock speed or speed of the Ram.
This improves the bus signal from normal DDR. This increases the overall transfer speed so that information is transferred faster. As well as the voltage and power consumption has been reduced. This means less power will be wasted which is useful for machines like servers that are on all the time.
The trend of reducing power consumptions continues with it being cut by 40% since the last iteration. The prefetch buffer width has also been doubled since last time which means that it can transfer the same amount of data in half the time of DDR2.
The reliability of data transfers is heavily improved with the addition DBI (Data Bus Inversion) and CRC (Cyclic Redundancy Check). This will improve the stability of the memory. The overall transfer rate has also been drastically improved.