1333 with 1600

Discussion in 'iMac' started by G4VHD, Mar 2, 2015.

  1. G4VHD macrumors newbie

    Mar 2, 2015
    I have just purchased a iMac 5k. It has 8 GB 1600 MHz DDR3 installed, but I have a spare 8 GB 1333 MHz DDR3 from old machine.

    I know if I install it I will limit the 1600 to 1333, so is this worth sacrificing for another 8g of ram?

    Thanks in advance.

  2. keysofanxiety macrumors G3


    Nov 23, 2011
    Nope, don't do it. The reason is that they're also different voltages. Although it will show as running at 1333MHz, this will cause a lot of performance problems and potential kernel panics (had it happen before with mixed RAM).

    Best thing to do is keep it all the same speeds.
  3. Nemic macrumors member

    Mar 18, 2012
    I'm not an expert so bear with me ;-)

    I have no idea if installing a different spec of RAM (as you suggest) will have a noticeable slow down effect. Or even if it may produce system instability. I guess there is only one way to find out.

    With RAM being rather cheap these days, I think you would be better off buying another 8GB stick of RAM with the exact same spec.

    If you do use the older RAM it may be possible to run some kind of benchmark to see if the lower specced RAM slows things down.

    Good luck.
  4. applebutter macrumors newbie

    Oct 30, 2014
    You probably shouldn't mix different ram sticks, but, if you do what you'll run into is that the faster ram will match the speed of the lower speed ram.

    Will you notice the difference? Not without some kind of benchmark you won't.

    Will it slow the computer down? Not that you will notice.

    Will it ruin the iMac no, but your mac could get real unstable.

    Put the ram in and test for stability.
  5. trevis macrumors newbie

    Mar 14, 2008
    Works for me

    I have had the similar combination (4+8) on 2011 iMac for more than a year.
    it works fine, no instability, no kernel crashes.
  6. redheeler macrumors 603


    Oct 17, 2014
    Don't do it unless you absolutely have need for more RAM. Otherwise it'll only make your iMac slower and less stable.

    If you're not sure if you need more RAM, go into Activity Monitor and click on the Memory tab during the tasks you usually perform. If Memory Pressure is colored green you do not need more RAM, and adding that RAM will only slow down your system.
  7. G4VHD thread starter macrumors newbie

    Mar 2, 2015
    Thanks for advice guys, dint see it until just though.
    Just having Photoshop and Aperture running and watching a 4k movie, running a second screen to the computer was struggling...bit disappointing really Apple selling a computer that isn't up to the tasks its made to do.

    Anyway, I've installed the extra 8gb, its made all the difference, running as I expected now.

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