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The following table compares the different types of memory. Note: All graphics are at 3/4 size.


SDRAM (Synchronous Dynamic RAM) DIMM

Notice the notch in the middle and the notch to the far left. SDRAM memory has 168 pins.


Notice the two notches in the middle, one in the center and one off to one side. RDRAM has 184 pins.

DDR (Double-Data Rate Synchronous Dynamic RAM) DIMM

DDR memory has a single notch, slightly off center. DDR memory has 184 pins.


DDR-2 memory differs from DDR memory as follows:

  • The notch is slightly closer to the middle.
  • It has more pins (240) than DDR memory. While you don't need to count the pins, you should notice that the pins are smaller because they have to fit in the same space as the DDR memory.


DDR-3 memory has a single notch off to one side, more off-center than the notch for DDR or DDR-2. Like DDR-2, DDR-3 has 240 pins.

144-pin SODIMM

SODIMMs are much smaller than other memory, perfect for notebook computers. Notice the notch slightly off center. 144-pin SODIMMs are used by SDRAM, DDR, and DDR-2 memory.

200-pin SODIMM

Notice the notch farther off center than the 144-pin SODIMM. You might also be able to notice the higher pin density. 200-pin SODIMMs are used by DDR-2 and DDR-3 memory.