dual channel DDR

Discussion in 'General Hardware' started by silky62678, May 14, 2003.

  1. silky62678

    silky62678 Guest

    Does the dual channel DDR work with the asus a7n8x deluxe if u have 3 sticks of ram installed? I know it works with 2 sticks but will it also work with 3 sticks of memory? all 3 sticks are 256 pc3200
     
  2. Blitzkrieg

    Blitzkrieg Guest

    No, you have to have either 2 or 4...hence dual.
     
  3. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    Yes and No.

    That motherboard uses the Nforce2 chipset.
    You will have 512MB in dual mode (aka the two 256MB chips). The third 256MB chip will not be in dual mode.

    You can even use RAM of different sizes and still have dual mode.
    For example, say you have a 256, a 512GB, and another 256.

    Then you will still have only 512 in dual mode (aka the 256MB chip and 256MB of the 512MB chip).
    The remaining 256MB of the 512 chip will be in single mode, and the other 256MB chip will be in single mode.
     
  4. Taurus

    Taurus hardware monkey

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    but.. most nforce2 boards have 3 slots (some just 2). i'm fairly certain you can have 2x256mb on one side and 1x512mb on the other have have full dual-ddr functionality.
     
  5. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    Only two of the three chips will run in dual mode, and then only the smallest amount of memory that the two chips have in common.

    In your example, you would have 2x256 chips in dual mode, and 1x512 chip in single mode.

    When it comes to chips of different sizes, here's a good explanation from Anandtech:
    http://www.anandtech.com/chipsets/showdoc.html?i=1654&p=3
     
  6. Taurus

    Taurus hardware monkey

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    i understand that. that's if you have..

    [_____256mb______]
    (gap)
    [_____128mb______]
    [_____empty______]


    i'm talking about...

    [_____256mb______]
    (gap)
    [_____128mb______]
    [_____128mb______]

    the gap is what splits the two channels. so wouldn't that lower channel be accessing 256mb total just like the upper one?
     
  7. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    I'm not sure if I'm understanding your question exactly, but maybe I can clarify what I mean a little better.

    On that second example, you have a total of 512MB on the system
    The nforce2 chipset only uses two of the 3 memory banks in dual mode. I do not know which ones they are. From what you are telling me, it is the first and the second one in your diagram, so we'll just assume that what it is for sake of illustration.

    In the two memory banks, one of them is 256MB and one is 128MB. The nforce2 chipset allows memory modules of different sizes, however it will only run an even amount on both pieces of RAM in dual mode.
    To put it more simply, you would only have 128MB on the 256 chip in dual mode, and all 128MB of the 128MB chip in dual mode. That's a total of 256MB in dual mode. The rest of the memory on your system would run in single mode (another 256MB)

    Here's a diagram based on the info you gave:

    This is the physical placement of the RAM sticks. The nforce2 chipset allows the ones in red to run in dual mode:
    [_____256mb______]
    (gap)
    [_____128mb______]
    [_____128mb______]

    This is a theorical representation of what actually happens to the system.
    Red represents memory that is running in dual mode; blue represents memory that is running in single mode.
    [_____128mb______][_____128mb______] = 256MB chip
    (gap)
    [_____128mb______] ................................... = 128MB chip
    [_____128mb______] ................................... = 128MB chip

     
  8. Sazar

    Sazar F@H - Is it in you? Staff Member Political User Folding Team

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    nicely put... :)

    makes a lot more sense than what I Was typing out lol...

    btw the general thing in computers is that items tend to lower down to the speed of the slowest component as well... hence ddr 2700 and ddr2100 in configuration would both run @ ddr2100 spec speeds...

    the advice would be to ensure the SAME memory in each channel if possible to maximise bandwidth and ergo.. performance...

    if you do not have similar mmeory.. sell off whatever disimilar components you may have and start anew with a common denominator... ie the 256mb clip or some such...
     
  9. silky62678

    silky62678 Guest

    So let me get this stright. 3 Dimm slots, lets say all 3 have 128mb pc2700. slot 1 and 2 are dual and the 3rd slot is single. if i have all 3 slots filled, slot 1 and 2 will still run the dual channel but the 3rd will work as single like it was designed to? are there any bad things of having both dual and single channel running at the sametime ?
     
  10. Sazar

    Sazar F@H - Is it in you? Staff Member Political User Folding Team

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    I would assume that in order to get max performance you will have to use 2 similar clips in the appropriate dimm slots... just because of the dual channel architecture...

    :)

    you can use 3 if you want but its not 'true' dual channel performance I would think... i.e. not maximized or efficient performance...
     
  11. Taurus

    Taurus hardware monkey

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    i'm aware of all that kevin, thanks. :)

    but i thought that the two lower slots counted as one channel... just like every other motherboard where all 3 or 4 slots count as one channel. so on an nforce2, you could have 1x256mb on the top... and 2x128mb on the middle and bottom. the 2x128mb would essentially be treated like 1x256 since they are on the same channel and you would have a full 512mb of dual-ddr.

    but if you're sure that the middle and lower slots can't be used together in a full dual-ddr configuration... that you can only use one or the other... then, i'm wrong. :huh:
     
  12. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    It's possible. I don't know if my explanation is right. I don't know of any place that specifically addresses that issue. Do you have any info on it?
     
  13. Taurus

    Taurus hardware monkey

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    none at all. it was just what i assumed all this time... but then other people believe otherwise, so i'm curious.
     
  14. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    I think you were right on the memory issue. I never found a site that gave the answer flat out (or maybe I did?).

    One site said that you could put 256 in the first slot and 2 128 modules in the other two to get dual mode (they didn't use exact numbers).

    So, that would mean the following:

    Diagram of RAM placement.
    Red = channel 1
    Blue = channel 2
    If you put the two channels together you get dual mode.
    [_____slot1______]
    (gap)
    [_____slot2______]
    [_____slot3______]

    The system with some RAM in there:
    [_____256MB______]
    (gap)
    [_____128MB______]
    [_____128MB______]

    Red channel (256MB) + Blue Channel (128+128) = 512MB in DUAL MODE!
     
  15. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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  16. LeeJend

    LeeJend Moderator

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    Interesting discussion.

    BUT one of the recent reviews I read (maybe at tomshardware?) said that the Dual DDR was not working well unless you have a matched set of DIMMs. That's 2 DIMMs same size, same speed rating (Mhz and CL), and same manufacturer.

    Anybody tried a mismatched set?

    As for which slots to use one of them is a different color put one DIMM there. Put the second DIMM in the next higher slot number.
     
  17. Kevin Ar18

    Kevin Ar18 OSNN Senior Addict

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    If you ever find the answer let us know :) and provide a link to :)
     
  18. Geffy

    Geffy Moderator Folding Team

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    how can you test it?