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New iMac, Upgraded Ram, But Ram Running @ 1333mhz

Discussion in 'iMac' started by Jazwire, Dec 14, 2012.

  1. macrumors 6502a

    Just got my new 2012 iMac set up, I ordered it with 16 gb (2x8) , and then purchased a Corsair Vengeance Kit from Amazon (the one several people have linked in here) it is 1600mhz ram I'm looking right at the box as I type.

    The model number of the ram confirms it is 1600mhz, CMSX16GX3M2A1600C10

    But when I go to "About this Mac" it does show correctly 32GB, but it's running at 1333mhz not 1600mhz.

    And if I go to Hardware/Memory it shows all 4 sticks running at 1333mhz.

    Any ideas???
  2. macrumors 6502a

    Maybe the RAM was spec'd wrong. Had it's setting clocked at the lower speed. I had RAM that was deactivated by an Apple Firmware update. Sent it back to the manufacturer (DataMem) and they flashed the settings and sent it back. Many happy years of service after that.
  3. WilliamG, Dec 14, 2012
    Last edited: Dec 14, 2012

    macrumors 603

    Have you tried with just the one pair? I believe they work in pairs, missing every other slot, so 1 and 3 are one pair, and 2 and 4 are the other (if I believe what I read in some other thread - I guess I don't know how they came from Apple?). I'm curious as to what happens when you use just the Apple RAM, and then just the Corsair RAM. Keep us posted, please!
  4. macrumors 6502a

    I checked with Apple on 11/30, and they confirmed my suspicion, and the commonly agreed upon position of several of us discussing it in another thread. Apple will have filled the first two slots with the base RAM, which are the first pair. The second pair is empty. You don't want to fill every other, leaving empty spaces in the middle.

    That said, I agree, he should take them and try each one in turn. He'd need to do them as matched pairs in the first two slots. Combinations of AB, AC, AD, BC, BD, CD will help him sort it out if there are one or two bad DIMMS.
  5. macrumors 603

    Good to know. Either way, I'd love to know what's going on here since I'm going to be using this very RAM in my soon-to-be-delivered iMac.
  6. macrumors regular

    Same here. I would be a little upset having paid a bit of a premium for this ram.
  7. macrumors 6502a

    He also might want to put the original RAM back in, either separately or during testing the others, and see what the speed reads on the 2x4GB.
  8. macrumors regular

    If you stick with Crucial or Kingston you can't go wrong.
  9. macrumors 6502a

    Well... here is the news. Not so good.

    The Corsair by itself ran @ 1600mhz
    The Stock Ram (Hynix) by itself ran @ 1600mhz

    When both are installed they run at 1333mhz.

    I even tried the ram in different slot configs.

    So not sure if its an issue when you get to 32GB it goes to 1333mhz or its because of mixing the ram brands.

    I guess I might just buy another 16gb of Corsair and see if that fixes it, or see if I can find that Hynix and buy that.

    Anyway...thats the verdict.
  10. macrumors regular

    Yea I read how picky some chipsets are with mixed brands. Just buy how ever much RAM you need from Crucial or Kingston and sell or don't use the other RAM you have.
  11. macrumors 601

    Hey William your everywhere mate :D

    I have this exact RAM purchased from amazon OP it is this one right? http://www.amazon.com/gp/product/B0076W9Q5A/ref=oh_details_o00_s00_i00

    So it won't work correctly, are you guys returning them? I'm clueless on this as far as hardware just wanted to pop them in I'm glad to have read this. I haven't got them yet will be here on Monday so I'll just not even open them.
  12. macrumors 6502a

    That is the ram I bought.
    So yes it works, but doesn't play well with stock ram.(if you plan on keeping the stock ram and adding this, it appears it will indeed underclock the ram.)

    Im not getting errors or anything, it just running the ram slower than it should be running.

    I am undecided on returning it , or just buying another 16gb as this ram is better than the stock, better timings etc.)
    I think I'm better off trying to get the same ram as Apple used (Hynix) if I can though.
  13. macrumors 6502a

    When you run the corsair alone does if switch back to 1600mhz how it should be ? Please let us know because I'm interested purchasing the 32gb and if it doesn't work as it should then can someone suggest something else that works as advertised ? Mac sales ???
  14. macrumors 6502a

    Yes the Corsair alone does run at 1600mhz, its only when I mix it with the stock ram it under clocks to 1333.

    So if you are going to run 32GB of the Corsair, I would suspect you will be fine.
  15. macrumors 6502a

    Cool, thanks for sharing the info. Are you going to order another 16gb pack? If you so please keep us posted just to make sure they do run well with the whole 32gb
  16. macrumors 6502a

    Did you try the ordering that WilliamG suggested? Just in case I (and logic) am wrong? I did check with Apple, but you never know if the rep I spoke with knew what he was talking about. Logically, it would make sense for the installed pair to be properly installed for maximum utilization, but stranger things have happened.

    Go ahead and see what happens when you go 8/4/8/4 and let us know.

  17. macrumors 6502a

    I already tried putting the ram in different slots.

    By default the stock ram in slots 1&3 , so I put the Corsair in 2&4.
    Then I tried stock ram in slot 1&2 Corsair in 3&4, and that made no difference.


    Actually I think I am going to order another set of the Corsair from Amazon , since I actually could use the stock ram I have now on another machine I have.
  18. macrumors 6502a

    Ok thanks please let us know how that goes since I almost bought that ram today I just want to make sure I want to make moneys worth I highly appreciate this info
  19. macrumors 6502a


    Just order 32GB of the same memory and it seems it will work fine. Sell the apple ram
  20. macrumors 6502a

    Yep just placed the order, should be here Monday. I'll update this thread with my findings. (Which I am sure will be it works fine if you use all Corsair.)
  21. macrumors 603

    Good to know it's just the mixing of brands causing the issue. Shame that happens, though. And it seems the stock RAM really does come in slots 1 and 3. Also good to know!

    And yes, I am everywhere, bahaha!
  22. macrumors 601

    I appreciate the info, so who's ordered RAM and combined it with the stock one having it clock at regular speeds? I hate to take it back and don't really need 32GB
  23. macrumors member

    I'm running 4x 8GB corsair vengeance on mine and it's running at 1600mhz.
  24. macrumors member

    Is both stock and cosair run at 1.5v for 1600mhz?
  25. macrumors regular


    Good info thanks for sharing.

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