Is this normal [RAM showing wrong speed]

Discussion in 'iMac' started by Mr. G4, Apr 12, 2013.

  1. Mr. G4 macrumors 6502

    Mr. G4

    Joined:
    Mar 29, 2002
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    Rohnert Park, CA
    #1
    I just got my iMac 27" Late 2012 with the original 2x4 GB and added 2x8BG Corsaire Vengeance CMSX16GX3M2A1600C10, all of them supposed to be 1600MHz but in the About this Mac it shows 24GB 1333 MHz...what's wrong with that?
     
  2. bflowers, Apr 12, 2013
    Last edited: Apr 12, 2013

    bflowers macrumors 6502a

    Joined:
    Jul 19, 2006
    #2
    A quick search would have helped. CMSX16GX3M2A1600C10 Your problem is in that last part. the "10" does not match what is in your machine. In really simplified terms, the RAM has to sync at a common frequency, which is slower than either set is capable of independently.

    Short answer, you got the wrong RAM!

    Here is a lengthy thread detailing the issue as it first came up. Later in the thread we discussed the problems. There were some very knowledgeable people contributing to the conversation. You will want to return that RAM and get the right kind.
     
  3. justperry macrumors 604

    justperry

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    #3
    A quick search does not help, I just tried and can't find much, you should explain why this is instead of just saying it doesn't.
    Most people don't know crap about those numbers, they just go to crucial for instance and they will figure this out.

    Now, I would like to know what the 10 stands for, I guess I have an idea (C10-C11) but would like to know, genuinely.
     
  4. iF34R, Apr 12, 2013
    Last edited: Apr 12, 2013

    iF34R macrumors 6502a

    iF34R

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    #4
    I already knew the ram would be downclocked when putting it in. What I did was removed the "stock" 2x4GB sticks, and I'm at 16GB with the Vengeance.

    When needed, I'll add another 2x8GB Vengeance pair.

    Its the timings basically. CAS Latency, or access times.

    When you pair RAM up, one with a better CL than the other, it has to "downclock" to the other RAM's supported timings.

    The stock ram that came with that iMac has CL11 and the Vengeance is CL10.
     
  5. Mr. G4 thread starter macrumors 6502

    Mr. G4

    Joined:
    Mar 29, 2002
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    #5
    Actually, I just found out the fault is from the Apple stock RAM, they are 1333MHz...Took them out and leave only the Corsair and now it shows 1600MHz. (Sorry iF34R, didn't read your reply before posting this).

    Thank you Apple, not only you over charge on the RAM price, you put "crap" in your machine that is not up to spec.
     
  6. eattherich macrumors 6502

    eattherich

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    Jul 8, 2011
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    Berlin
    #6
    No, the standard RAM in the late 2012 iMac will have been 1600MHz. It will just have shown at 1333MHz due to the incompatibility of the two different memory modules.
     
  7. Mr. G4 thread starter macrumors 6502

    Mr. G4

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    #7
    Granted, but for the price they charge us....
     
  8. iF34R macrumors 6502a

    iF34R

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    South Carolina
    #8
    Agreed. I can't think of any reason to buy the RAM from Apple. Even if you had to put 32GB in the iMac, you would do if for 1/3, or less, than the cost Apple gives.
     
  9. xraydoc macrumors demi-god

    xraydoc

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    Oct 9, 2005
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    #9
    Buying high-spec RAM generally used for custom PC builds can cause problems with Macs unless you're certain you're buying RAM with exactly the correct specs.

    Personally, I buy RAM tested specifically for Mac compatibility in the machine for which I'm buying it. Buying something with higher specs will not make your Mac faster, and more than likely cause problems like in the OP.
     
  10. bflowers macrumors 6502a

    Joined:
    Jul 19, 2006
    #10
    I did, they are not the same speed, I believe it has something to do with the latency. The lower the number, the better, but when they don't match, they seem to need to find a common frequency. Therefore, you get a slower speed than either is capable of on its own.

    The stock RAM is fine, you simply bought RAM with different timings. I purchased stock RAM from another forum member, stuck it in my machine with my original stock RAM, and get 1600. There is nothing wrong with what Apple provided.
     
  11. drambuie macrumors 6502a

    Joined:
    Feb 16, 2010
    #11
    There is nothing substandard about the OEM Apple RAM. The standard timing for 1600MHz RAM is CL11. Anything faster than CL11 at 1600MHz is considered overclocking. The Corsair Vengeance is overclocking RAM. The fastest timing (CL10) will prevail, and since the Apple RAM is only spec'd for 1333MHz at CL9 or CL10, the CPU memory controller will downclock to 1333MHz, to accommodate the slower RAM. If you want 1600MHz at CL10, obtain more Vengeance to replace the OEM RAM.
     

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