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Need Help with Dual-Channel Memory (DDR2)

Discussion in 'Hardware' started by AhrenBa, May 22, 2007.

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  1. AhrenBa

    AhrenBa Thread Starter

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    Hello,

    I have a Dell 4700 Desktop with two sticks of 256MB (PC2-3200) DDR2 RAM. These are installed in the 1 and 2 DIMMs in order to take advantage of Dual channel memory.

    However, I am planning of adding two more [different] sticks (1GB each) to DIMM slots 3 and 4. Will the system still take advantage of the dual channeling, in this setup?

    Also, I am wondering greatly if I buy this new RAM, and it operates at PC2-4200, 5200, or 6400, will this disable the dual channel? What PC-xxxx RAM should I go for?

    Also what is a good CAS latency to look for on RAM? What exactly does the PC2-xxxx number refer to?

    Thank you.
     
  2. Rich-M

    Rich-M

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    2.5 -3 would be the best cas latency...but something makes no sense if your board had dual channel capability then the ram would be in 1 and 3 not 1 and 2 slots.
    For dual channel ram you only need that each set be identical.
     
  3. 2lazy2care

    2lazy2care

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    Check the motherboard manual (on the manufacturer's website) to see how the ram should be installed to still use dual channels. Usually if 1 & 2 are a pair then 3 & 4 will work with dual channel as well.

    Just make sure you keep the pairs together. For example the old sticks on 1 & 2 and the new ones on 3 & 4, don't mix them or you could have problems.

    As for the speeds it will not disable the dual channel but you could run into problems. I would recommend you get new ram to match the speed of your old ram but it's not necessary and it shouldn't disable the dual channeling. What most likely would happen would be the fastest ram might slow down to match with the slow ram.

    P.S. Sometimes computers have trouble recognizing all of the new ram if it's bigger then the old ram. So I would put the new 1GB sticks in slots 1 & 2 and the old ones in 3 & 4.
     
  4. The Jesbus Fire

    The Jesbus Fire

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    You guys are also missing the fact that he's trying to mix DDR2 and DDR.

    Hey-O!

    Check your motherboard to determine the Max amount and speed of ram your system can handle. If it's PC-3200 then you can only buy PC-3200 cause it's DDR.

    PC2-4200, 5200, and 6400 are all DDR2.

    Also when installing your RAM, you always install the largest amount in the first DIMM otherwise it will tone down your other memory.

    Dual channeling also only works if you use the same type of ram at the same latency. I think it's only per 2 banks anyways. But still, install the 2 gig sticks of probaly pc-3200 in slots 1 and 2, then put the other ones in 3 and 4. You may have to adjust the timings in the bios depending on what type of sticks you buy.

    Personally I'd just get the 2 gig sticks and not even worry about the 256 sticks. 2.5 gigs of ram, 2 gigs of ram, what's the difference?
     
  5. accat13

    accat13

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    Hmmm from the DEll site Tech specs 4700 series

    "400-MHz (PC2-3200) and 533-MHz (PC2-4300) DDR2 unbuffered SDRAM non-ECC"\
    4 slots....4 gigs max

    "Always install DDR2 memory modules in the order indicated on the system board.

    The recommended memory configurations are:

    o A memory module installed in connector DIMM connector 1

    or

    o A pair of matched memory modules installed in DIMM connectors 1 and 2

    or

    o A pair of matched memory modules installed in DIMM connectors 1 and 2 and another matched pair installed in DIMM connectors 3 and 4

    NOTICE: Do not install ECC memory modules.

    * If you install mixed pairs of DDR2 400- and 533-MHz the modules function at the slowest speed installed.

    * Be sure to install a single memory module in DIMM connector 1, the connector closest to the processor, before you install modules in the other connectors."

    I suggest that you goto the DEll web site and read the manual

    http://support.dell.com/support/edocs/systems/dim4700/sm/index.htm
     
  6. The Jesbus Fire

    The Jesbus Fire

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    My mistake I thought PC-3200 only came in DDR, but it's actually DDR2. Learn something everyday.
     
  7. AhrenBa

    AhrenBa Thread Starter

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    Thanks for the suggestions, Rich-M. I appreciate it. What I actually meant was that the arrangement of the DIMMs are 1-3-2-4. This way the RAM matches with 1 and 2, and 3 and 4.

    Very good point, thank you!

    Thanks for the links, accat13.


    No problem! Thanks for the help.

    Also, I have one more question. Is there a specified limit on the PC2-xxxx (mhz) that a computer will take?

    Also, I found this in the documentation:
    [​IMG]

    Does this mean my Dell 4700 can only support up to PC2-4200 (533Mhz) RAM? If so, what would happen if I installed something like PC2-5200 RAM in my system? Would it clock it down or just not work?
     
  8. accat13

    accat13

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    From the dell site it seems to be 533-MHz (PC2-4300) if you mix speeds it will revert to the lower speed....So if you leave your original sticks in the pc any new sticks bought will run at the speed of your original(PC2-3200 256*2)
     
  9. AhrenBa

    AhrenBa Thread Starter

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    Thank you for the response. However, what I was trying to figure out was whether my computer could support the higher RAM (PC2-5200 and above). From that picture I provided in the post above, it says something about PC2-4200, but when I check Crucial's scanner, it gives me the option to buy the higher rated RAM above PC2-4200.

    Can my PC actually support this RAM? I understand that it will clock to the lower speed if I leave the old RAM in, but will it allow the PC2-5200 and above RAM to operate a full speed, or even work for that matter, if I remove the old RAM?

    Here is the image again, and here is the link.
    [​IMG]
     
  10. AhrenBa

    AhrenBa Thread Starter

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    Shoot, I hate to bump topics...

    Could someone attempt to answer my question in post #9? Thank you very much. :)
     
  11. crjdriver

    crjdriver Moderator

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    When you mix ram, there are really no cut and dry answers. You need to try the config and see if it works. There is a reason most board makers have an "approved list" for ram; it has been tested and found to work.

    FWIW IMO when you mix ram types, speeds, etc you are asking for a problem.
     
  12. AhrenBa

    AhrenBa Thread Starter

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    Ok, thank you for your answer.

    What I am trying to figure out now is if my Dell 4700 will support something like PC2-5200 RAM (refer to the image in the post above)? If I take out the current RAM and put in PC2-5200 will my computer support it? If my computer only maxes out at PC2-4200 what will happen if I put in 5200 or above? Wil it scale it down. Remember, in this situation, this is with the old RAM taken out. Thank you.
     
  13. crjdriver

    crjdriver Moderator

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    The quickest and easiest way to see if your system will support the faster ram is to go to crucial's site and input your system. It will show ALL compatible ram AND guaranty that it will work.
    I just checked dell's site for you and it lists pc5300 ram so I would say yes it will work.

    Note there are three different 4700s so it would be a good idea for you to check with your exact specs.

    Again I would not mix the ram; just buy new whatever amount you want ie 1gig, 2gig, etc. Mixing ram is a bad idea and often induces stability problems.
     
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