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Question about DDR RAM in meyers book

Discussion in 'A+' started by fish79, Mar 5, 2008.

  1. fish79

    fish79 New Member

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    Hi,

    I was a bit puzzled by dual channel DDR Ram. Is DDR ram on dual channel mode supposed to run faster than in single channel mode, if this is correct why?. It doesn't make any sense to me.:blink

    regards
     
  2. tripwire45
    Honorary Member

    tripwire45 Zettabyte Poster

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    According to Wikipedia:
     
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  3. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    DDR and dual channel aren't the same thing.

    Dual Channel is a way of banking 2 DIMMs together with interleaved access which means that the combined memory is faster than just using one DIMM. To get this to work you must have a motherboard that supports it, and closely matched pairs of DIMMs, and fit them to the correct sockets. Most motherboards colour-code the sockets to assist with this.

    Harry.
     
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  4. greenbrucelee
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    greenbrucelee Zettabyte Poster

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    The guys are correct on both counts.

    If you look at your mobo manual or at you mobo you will see the colour of your RAM slots some will be different. In my mobo I have blue & yellow slots. The blue ones take dual channel ddr2 RAM and the yellow ones take dd2 ram in single channel mode.

    I have 3GB RAM in my PC 2 matched pair of DDR2 RAM in the first two slots then a slot free then 1GB in the last slot.

    I have never tried just running with the two matched pairs but I know the latency (speed) would be faster with 2 GB matched pairs than 2 matched pairs and 1GB, I may have a look at the difference this weekend if I can be bothered.

    EDIT: just so you know in the RAM chapter review questions where it asks you about the difference between DDR & DDR2 where it shows you the correct answer it says its B but gives you the explanation for C. C is actually correct.
     
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  5. fish79

    fish79 New Member

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    Thanks! I think I understand now, dual channel mode doesn't increase ram clock speed but can lower latency.
     
  6. greenbrucelee
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    greenbrucelee Zettabyte Poster

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    2 matched pairs dual channel eg 2 x pc 6400 800MHz is faster than 2 single channel pc 6400 800MHz dimms.

    I'll use my mobo as an example again if I putt the two 800MHz dimms in the first two slots which are blue then they will run in dual channel mode i.e faster but if I take them out and put them in the yellow slots next door then they will run in single channel mode i.e slower.
     
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