pairing RAM into mutliple sticks

Discussion in 'iMac' started by chris1184, Jul 12, 2011.

  1. chris1184 macrumors regular

    Joined:
    Apr 26, 2011
    Location:
    Chicago
    #1
    OK I have been researching a little bit here and there...is it bad for me to do this - put in a single 4gb stick of RAM into my mid 2011 iMac which already has 4gb of RAM in two - 2Gb modules? I saw some things using google of people saying it doesn't really matter, while others say that it would be better to have 2 -2gb sticks instead of 1- 4gb stick...can anyone chime in? i mean i won't take a performance hit will I? also i can always just order another 4gb stick so that i have a total of 12gb's of ram instead of 8...but before I do that can I still just use the single module along with the 2 factory ones?
     
  2. phlydude macrumors regular

    phlydude

    Joined:
    Jun 21, 2010
    Location:
    Newark, DE
    #2
    i believe that the RAM in the new iMacs are supposed to be dual channel...so I would say try it if you want but be prepared to have another 4GB stick on hand...for ~$55 on sale, you can get 8GB (2x4GB) - not a mightily expensive upgrade option if you are intent on upgrading down the road (which I assume is what you are planning by opening RAM slots)
     
  3. 3lfk1ng macrumors newbie

    Joined:
    Jul 12, 2011
    Location:
    Santa Barbara, CA
    #3
    I think people just aren't clearly explaining to you Dual-Channel memory.

    Basically your computer uses a 2x2gb matched pair configuration to take advantage of Dual-Channel. Think of it kind of like how a Dual Core processor works; two "things" working together at the same speed to get the job done twice as fast.... in theory.

    If you only add 1 stick of 4gb in one of your two empty slots. That would put you at 8GB of ram, which will certainly speed things up for the computer (having more to play with and all), but it could in theory hamper your performance a little because now dual-channel could be disabled. The reason I say "could" is because most of the newer Intel chipsets can run "flex" which means that it will look for two matching pairs (2x2gb) and run those in Dual-channel mode and run the remaining ram that has no pair in single channel and cycle ram information based on priority.

    In most real world applications you will not notice a difference. Typical benchmarks have shown that Dual-Channel really only offers a 5% gain over single channel. Things get a little more complicating with latency timings and triple channel.

    I say don't worry about it. Go for a single stick of 4gb and run it alongside your 2x2gb.
     
  4. chris1184 thread starter macrumors regular

    Joined:
    Apr 26, 2011
    Location:
    Chicago
    #4
    thank you very very much for that answer...great reason I keep coming back and learning more and more from here...do u know if there is utility or application i would be able to run to test if my iMac is running in dual channel mode or flex after the upgrade?
     
  5. 3lfk1ng macrumors newbie

    Joined:
    Jul 12, 2011
    Location:
    Santa Barbara, CA
    #5
    No problem, glad to help.

    I'm currently not aware of how to check for this within Mac OSX, perhaps someone else could chime in. I just recently made the switch to Mac for programming after years of building and overclocking PC's for benchmarking and gaming.

    If you have a Windows partition you can download CPUZ and it will tell you what configuration your ram is running.
     
  6. phlydude macrumors regular

    phlydude

    Joined:
    Jun 21, 2010
    Location:
    Newark, DE
    #6
    Because of links like you posted or links like this:
    http://tinyurl.com/6dwlbuo
    There should be no reason to have to explain dual-channel memory to someone... :)
     
  7. chris1184 thread starter macrumors regular

    Joined:
    Apr 26, 2011
    Location:
    Chicago
    #7
    lol kiss my :apple: the way in which he explained it was awesome..besides sometimes when i google i get sent here to these forums so why not just ask if it's still not clear...anyway thanks for the chuckle
     
  8. 3lfk1ng macrumors newbie

    Joined:
    Jul 12, 2011
    Location:
    Santa Barbara, CA
    #8
    There is a difference between explaining something in a way that is quick and easy to understand and offering someone (or other interested members of this forum) an immediate link to an article so that one can read a much more in-depth understanding of how dual-channel memory functions should it pique their interest.
     
  9. chris1184 thread starter macrumors regular

    Joined:
    Apr 26, 2011
    Location:
    Chicago
    #9
    Installed the 4GB memory module last night...super easy, super fast install. Everything works as normal...don't know if it's my mind playing tricks on me but it seems like some things are quicker....ie - launching applications, saving files, exporting stuff from Garageband to iTunes...didn't get too much time to play with it last night after the install but will put it through it's paces tonight
     

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