Quick Memory Question

Discussion in 'hardware' started by philby, Sep 20, 2010.

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  1. philby

    philby Registered Member

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    Hello All

    I was just looking at a Vaio spec. today and noticed that it had 6GB DDR2 on board, split into 1x2GB and 1x4GB.

    I would have bought the machine but was unsure: My very basic (mis-)understanding of memory module array was that if memory is to be run optimally in dual channel mode, it should be run in equal pairs, so I was surprised by this pairing.

    Is it OK then to run a 2 GB stick alongside a 4GB stick? I've had a read about it, but it's all a bit beyond me to be honest.

    Thanks in advance

    philby
     
  2. Cudni

    Cudni Global Moderator

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    that was my understanding too so as a guess i would say that it is ok to run 2 + 4 combo with maybe minimal loss of optimal performance (assuming it is even noticeable)
     
  3. philby

    philby Registered Member

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    Yes, I mean I'm sure Sony know what they're doing (?), but why not just spec. 2x3GB side by side, I wonder...

    philby
     
  4. Cudni

    Cudni Global Moderator

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    it could be that the ram is only produced in 1, 2, 4GB sizes. Better to have 2 x 4 :)
     
  5. philby

    philby Registered Member

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    Exactly! Just wish I could afford that!

    Maybe you're right that they don't produce 3s...

    Thanks for answering: glad to know I wasn't way off the mark with the equal pairs thought.

    philby
     
  6. YeOldeStonecat

    YeOldeStonecat Registered Member

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    Memory is now so fast, even if you don't have matching pairs running dual, the slight slight loss in speed isn't as much of a bottleneck as it was, the FSB is still pretty much the bottleneck, and actually what's more of a limitation in laptops is their typically slower hard drives. Having unmatched pairs in laptops is very common.

    So while running some synthetic benchmark on your memory would show something like a 15% drop in memory performance when doing unmatched pairs, in the real world...the benefit from having the extra 2 gigs for Veester/Win7 is more than offsetting the slight drop in memory speeds.
     
  7. Bill_Bright

    Bill_Bright Registered Member

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    First, you did not tell us the model number of your notebook so we have no way of verifying if that motherboard (or chipset, actually) even supports dual-channel. It may not, and if that is the case, the mis-match is immaterial, the RAM will run in single-channel mode. But 6Gb, regardless the mode, is still a lot of RAM and will provide excellent performance.

    Second, many motherboards support what Intel calls, "Flex Mode" (or "Flexible Dual-Channel" for SiS chipsets). This mode supports dual channel with mismatched pairs. Basically, using your RAM as an example, the first 4Gb will run in dual-channel mode, and the last 2Gb will run in single channel.


    Desktop Boards
    Single, dual, triple and flex memory modes


    Note also that, contrary to popular belief (most likely propagated by RAM maker marketing weenies), to operate in dual or triple channel mode, the RAM does NOT need to be of the same brand, timing, or DDR speed.
     
  8. philby

    philby Registered Member

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    Sorry Bill - I was browsing a new model and, perhaps incorrectly, assumed that all modern chipsets supported dual-channel.

    Thanks to you both for all the info!!

    philby
     
  9. Bill_Bright

    Bill_Bright Registered Member

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    No problem. Note that most do support dual but many now support triple channel too. That said, since you did not specify which Vaio you were talking about, we could not tell what that board supported, or if it was even a "modern" system you were looking at.
     
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