DDR SDRAM

Double Data Rate Synchronous Dynamic Random Access Memory, or DDR SDRAM, is a type of memory microcircuit commonly used in computer processors. It is the later improvement over regular Synchronous Dynamic RAM, also known as Single Data Rate SDRAM (SDR SDRAM).

Advantages of DDR SDRAM

The following are some of the advantages DDR SDRAM has:

  • DDR SDRAM can achieve two times as much the bandwidth (bit rate) compared to the SDR SDRAM through double pumping. This means moving data on both edges (rising and falling) of the clock signal without changing the frequency of the clock and implementing the burst-mode-data-transfer.
  • DDR-SDRAM consumes less power. That is why it is specially suited for notebook computers.
  • It has the capacity to transfer data 64 bits at a time at 100 MHz bus frequency. You can get the maximum transfer rate of DDR SDRAM by using the formula below:
  • Transfer rate = (memory bus clock rate) x 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte)

    Transfer rate = 100 MHz x 2 x 64 / 8
    = 1600 megabytes/second (maximum transfer rate)

Different Alternatives

  • DDR2 SDRAM outdated the DDR SDRAM. Though it works with the same principle as that of the DDR SDRAM, DDR2 SDRAM developed several modifications to facilitate higher clock frequency.

    The pre-fetch buffer width of DDR SDRAM is only 2 bits compared to the 4 bits deep of DDR2 SDRAM. Despite the successful clock speeds of DDR2, the general performance was no greater in the early implementations because of its high latencies. It gained public attention by the end of 2004 when lower latencies became available.

  • Rambus XDR DRAM, which is a competing product of DDR2 SDRAM, is another alternative to DDR SDRAM. However, DDR2 SDRAM has become the standard because XDR lacks hardware support.
  • DDR3 SDRAM superseded DDR2 SDRAM and became the new standard and an alternative for DDR SDRAM. It provides new features and even faster performance.
  • The Rambus Dynamic RAM can also be an alternative of DDR SDRAM. However, it is expensive compared to other memory chips and most producers dropped their support to their chipsets.