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DDR Memory organization

  1. Sep 18, 2012 #1
    I was going through the datasheet of 1Gb DDR2 SDRAM. It's organized in rows, columns and banks.
    The 1Gb is actually 64Mb*16 datalines.
    Which is 8Mb*8 Banks * 16 data lines
    I can't figure out how they got 8Mb?

    In the datasheet block diagram (attached), there are 13 row address lines. So 2^13 = 8k
    there are 8 column addr lines, so 2^8 = 256
    8192*256 = 2Mb ???

    Attached Files:

  2. jcsd
  3. Sep 18, 2012 #2


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    Science Advisor

    Hi likephysics. Each bank is actually organized as 8192 by 256 by 64 bits. There are 10 column select bits, but only 8 of them are used to actually select the column. The remaining 2 are used to select the correct 16 bit word from the 64 bit bank output.
  4. Sep 20, 2012 #3
    uart, Thanks.
    One more DDR question - why do you need to precharge a row before selecting it?
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