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    6GB Dual Channel Ram? (XPS 16)

    Discussion in 'Dell XPS and Studio XPS' started by gpig, Apr 14, 2010.

  1. gpig

    gpig Notebook Deity

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    The XPS 1645 offers choices of 4, 6, and 8GB of ram. Just out of curiosity, how can 6GB of ram be dual channel? I was under the impression that dual channel requires matching pairs, and that 6GB of ram would be one 4GB stick and one 2GB stick. However, the Alienware laptop seems to have listed what I would expect (3 and 6GB configurations not listed as dual channel). See below.

    [XPS 1645]
    4GB Shared Dual Channel DDR3 [Included in Price]
    6GB Shared Dual Channel DDR3 [Add $225.00]
    8GB Shared Dual Channel DDR3 [Add $375.00]

    [Alienware M15x]
    3GB DDR3 at 1066MHz [Included in Price]
    4GB Dual Channel DDR3 at 1066MHz [Add $50.00]
    6GB DDR3 at 1066MHz [Add $200.00]
    8GB Dual Channel DDR3 at 1066MHz [Add $350.00]
     
    gpig, Apr 14, 2010
    #1
  2. XmDXtReMeK

    XmDXtReMeK Notebook Consultant

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    umm there are 3gb sticks you know.
     
    XmDXtReMeK, Apr 14, 2010
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  3. ZippoMan

    ZippoMan Notebook Evangelist

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    O Rly? Can you provide a link? Thanks.
     
    ZippoMan, Apr 14, 2010
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  4. nk290

    nk290 Notebook Consultant

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    The OP is right in that the XPS 1645 uses one 4gb and one 2gb memory stick, and is dual-channel. I'm not familiar with the specifics, but I know it has something to do with the way the system handles the memory.
     
    nk290, Apr 14, 2010
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  5. Mechanized Menace

    Mechanized Menace Lost in the MYST

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    there is no such thing as a 3gb stick :D
    3GB=(1x1GB+1x2GB)
    4GB=(2x2GB)
    6GB=(1x2GB+1x4GB)
    8GB=(2x4GB)
    unless your using triple channel it would be
    3GB=(3x1GB)
    6GB=(3x2GB)
    9GB=(2x4GB+1x1GB) but I don't think this would be triple channel
    12GB=(3x4GB)
     
    Mechanized Menace, Apr 14, 2010
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  6. XmDXtReMeK

    XmDXtReMeK Notebook Consultant

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    XmDXtReMeK, Apr 14, 2010
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  7. Fusel Wusel

    Fusel Wusel Notebook Consultant

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    And you have actually noticed, that your "3gb sticks" are 3x1gb?
    There are no 3gb sticks. Neither for desktops nor for notebooks. ;)

    As far as I know the dual channel technology only depends on actually having two sticks...
     
    Fusel Wusel, Apr 14, 2010
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  8. funky monk

    funky monk Notebook Deity

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    Lol, fail. RAM works in powers of 2, and you're not allowed to use non intergers as powers :p

    But, although it's reccomended to have matching pairsif you want dual channel there are acceptions. If you're building a PC it's generally advisable to get two compleetly identical sticks to make sure it will run in dual channel (some brands don't like each other).
     
    funky monk, Apr 14, 2010
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  9. slikdealor

    slikdealor Notebook Consultant

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    i upgraded the ram on a studio xps 1645, and i went from 6gb (which was installed) to 8gb.

    the 6gb that was installed was 1 4gb stick and 1 2gb stick.

    what was odd was that they were 2 different brands (elpida and hynix).
     
    slikdealor, Apr 14, 2010
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  10. funky monk

    funky monk Notebook Deity

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    Dell just goes with whatever option is cheapest at the time, if the lowest prices for the different sizes come from different brands then they'll use different brands
     
    funky monk, Apr 16, 2010
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  11. tenknics

    tenknics Notebook Evangelist

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    If you referring to ram being only installed in pairs when you say "ram works in powers of 2"? then you are wrong. It depends on how many channels the chipset/chip support. The only reason we are installing in pairs is because the memory controller we have supports UP TO dual channels. With Bloomfield/Nehalem/Westmere based desktop and server chips they use a three-channel memory controller and ram in this case works in powers of 3. If you have a cpu with a single memory channel than it works in powers of 1.
     
    tenknics, Apr 16, 2010
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  12. Fusel Wusel

    Fusel Wusel Notebook Consultant

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    Installation in powers of two would mean, you could install 0,1,2,4,8,16... bars. In Powers of 3 would mean 0,1,3,9,27... bars. That can actually not be right if you think about it.
    He obviously means the size of the Ram, which actually works in powers of two. This is why there are no sizes like 3gb or 5gb etc. Only powers of 2. so e.g. 1024, 2048, 4196 etc. ;)
     
    Fusel Wusel, Apr 16, 2010
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  13. tenknics

    tenknics Notebook Evangelist

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    That is why in the first line I was asking in a way what he meant, and if he did mean it that way it was wrong and explained why. No harm done. Thanks for the clarification though :)
     
    tenknics, Apr 16, 2010
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  14. Fusel Wusel

    Fusel Wusel Notebook Consultant

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    Clarification was all I wanted :)

    And I have read about Dual Channel Technology on german wikipedia. I states, that e.g. newer Intel Chipsets have the capability to run asymmetric dual channel. That means, if you have two sticks, one with 2gb and one with 4gb, the chipset addresses 2x2gb dual channel and the remaining 2gb single channel.
    If you'r chipset is not capable of asymmetric dual channel, it adresses only single channel, if you have two different modules installed.

    So if you got an 64bit (x86-64) CPU, which has a bus of 64bit, you get a bus of 128bit width on dual channel and with that double the throughput.

    Thats it, I think :)
     
    Fusel Wusel, Apr 17, 2010
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  15. heheman3000

    heheman3000 Notebook Enthusiast

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    Nice explanation, finally someone who makes a reasonable argument from the facts rather than making up obscene ideas (such as 3GB sticks or installing RAM in powers of 3 LOL)

    FYI: Triple-channel = install ram in matching sets of 3, not powers of 3, so you can have 3x2GB plus 3x1GB for 9GB addressable.
     
    heheman3000, Nov 2, 2010
    #15