What are the four categories of DDR memory and how do they compare with regular SDRAM and each other?

Question

What will be an ideal response?

Answer 1

Double Data Rate SDRAM (DDR SDRAM, or SDRAM II, or simply DDR) is an improved version of SDRAM. DDR runs twice as fast as regular SDRAM, has one notch, and uses 184 pins. Instead of processing data for each beat of the system clock, as regular SDRAM does, it processes data when the beat rises and again when it falls, doubling the data rate of memory. If a motherboard runs at 200 MHz, DDR memory runs at 400 MHz. Two other improvements over DDR are DDR2 and DDR3. DDR2 is faster and uses less power than DDR. DDR3 is faster and uses less power than DDR2. The trend continues with DDR4 being faster and using less power than DDR3. Both DDR2 and DDR3 use 240 pins, although their notches are not in the same position. They are not compatible, and the different notch positions keep someone from installing a DDR2 or DDR3 DIMM in the wrong memory slot. DDR4 uses 288 pins.