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Late 2009 Core i5 & i7 iMacs OWC MaxRAM Certified To 32GB Of Memory

Tuesday, March 5th, 2013 | Author:

The OWC Test Lab technicians have been at it again. After hearing a few forum whispers of 32GB of memory working in the Late 2009 iMacs, we started our own investigation into the matter.

To be honest, we weren’t very optimistic on this rumor as, by specification, the Intel processors used in these machines list a maximum of 16GB of total memory…and our initial OWC MaxRAM Memory Certification tests didn’t pass.

We started our testing with the base Core 2 Duo (iMac10,1) model and have indeed confirmed that the Core 2 Duo models max out at 16GB of memory. When more than 16GB of memory is installed in those systems, the machine just would not complete booting. The prospect wasn’t looking too good.

But then we tested the other end of the spectrum with the 2.8 GHz Core i7 (iMac11,1) model and that is when the testing started to tell a completely different story.

Not only would our 32GB PC3-8500 DDR3 1066MHz SO-DIMM Memory Upgrade Kit boot the machine, but our testing uncovered that the machine was able to fully utilize all the RAM without any slowdowns. After testing our way through all the different models and all the different iterations of OS X that are compatible with these iMacs, we concluded:

The quad-core Intel i5 & i7 iMacs were able to address and fully utilize 32GB of OWC memory when running 10.6.3 or later once the latest updates were applied.

There is one caveat for those running 10.6.x – you MUST be running 64-bit mode in order to address all 32GB. In 32-bit mode, all 32GB will show, but only 16GB will be utilized. See our post Just Say “Know” when it comes to Snow Leopard’s 64-bit mode for more details on 32-bit vs. 64-bit mode.

OWC MaxRAM Testing in progress under OS X Snow Leopard.

OWC MaxRAM Testing in progress under OS X Lion.

OWC MaxRAM Testing in progress under OS X Mountain Lion.

How do you ensure your Late ‘09 iMac can address 32GB of RAM?

Check the Model ID of your iMac. If it is iMac11,1 simply run Software Update to make sure you have the latest version of OS X 10.6, 10.7, or 10.8 with any accompanying firmware updates.  We recommend keeping these up to date regardless of whether or not you intend to upgrade to 32GB.

Then, you just need the proper specification of memory modules such as the OWC 32GB PC3-8500 DDR3 1066MHz SO-DIMM Memory Upgrade Kit. It’s that easy.

And, yes, the additional memory is available to Windows via Bootcamp, too.

As always…Happy Upgrading!

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    1. Jay says:

      Will a higher PC3 12800 work for 09 2.8mhz quadcore 2374?

      • OWC Ben says:

        We only recommend 1066mhz modules for the late 09 iMacs. 1600mhz modules theoretically should down clock to the iMac’s 1066mhz speed though.

      • James Wages says:

        I ultimately purchased 1333MHz RAM for my late 2009 iMac 2.8GHz i7 Quadcore, despite the fact Apple does not claim to support it and despite OWC’s cautionary words. For the past 10 months it has been working fine, with no crashes or overheating issues at all. I ran benchmarks before and after which show greater performance after my upgrade to 1333 RAM, which seems to prove the 1333 RAM is indeed being clocked at 1333 and not being down clocked to 1067. I posted further details on Apple’s forum here:


    2. Harry Arthur says:

      I have a late 2009 27″ iMac 11,1 2.8 GHz Core i7, upgraded with OS X 10.9.2 Mavericks. I assume this machine will also run 32 GB upgrade kit specified above, though the article was written prior to Mavericks’ release. It is, of course, later than 10.6.3.

      Not familiar with EFI, but I assume from the article that this is upgraded automatically when the OS is upgraded/updated.

    3. Dom says:


      I have an iMac 27 11,1.
      I am running latest update of Lion 10.7.8, and there is no EFI update avail.
      So I understand I should be all set correct ?

      Also, the reason why I am looking for an upgrade is that after years of running fine, the machine started to reboot spontaneously. I understand these are often RAM issues. Is that your opinion ?

      I have installed 16GB of 3rd party RAM 3 years ago.
      So may be it is starting to go … ?

      Thank you for any feedback. I understand you can’t say for sure that this is the problem, but any “opinion” would be appreciated.

      Thank you!

      • OWC Eddie says:

        8Gb sticks will work in an iMac 11,1 with an iCore 5 or iCore 7 processor. 8GB sticks will not in an iMac that is running iCore 3.

        Defective RAM can be one of many components that can cause a machine to spontaneously reboot. I would recommend running a 3 loop test on your RAM with Rember.

        If you would like additional support, we encourage you to contact our technical support department via live chat, or email, or by telephone at 1-800-275-4576 | 1-815-338-8685

    4. Raul Felipe says:

      Hello, I work on a 2.8 GHz Core i7 iMac (iMac11, 1) 8Gb RAM, Snow Leopard with 64bit architecture on, and I would like to upgrade to 32gb of RAM.
      I have read that to do this I need to have the latest EFI installed and do not know what is this version I need and where to find it. I tried downloading the update iMac (27-inch) – EFI Firmware Update 1.0 but can not find it in the apple help page.
      Then I need to know, what is the version of EFi I need to have installed to upgrade my iMac to 32Gb of RAM?
      And, I can buy 32.0GB (4 x 8.0GB Kit) PC3-8500 DDR3 kit for Late 2009 iMac11, 1 models from europe?
      Thanks, excellent help and website.

      • OWC Ben M says:

        Good questions here. You can check the latest firmware for your iMac here – http://support.apple.com/kb/HT1237. That link also has the links to download the latest firmware. Firmware updates should be automatically downloading through your software updates as well.

        The European iMac11,1 should have no issues with the 32gb of memory if the appropriate OS and firmware are on it.

    5. John Nagy says:

      I have an 11,1 iMac with Intel Core i-5 processor currently running 16GB RAM, and Mountain Lion 10.8.4
      According to this post, I should be able to upgrade to 32GB RAM.
      If I upgrade to 32GB RAM, will this be available to Parallels?
      Under Parallels I am running Windows System 7 in 32 bit mode.

    6. Anah says:

      I just upgraded the ram from your 16gb kit and it works like a charm! Yay! I have the late 2009 iMac i7 model and now it is showing:

      Memory 20GB 1067 MHz DDR3.

      I’ll upgrade to 32gb when the budget permits but right now, it is soo fast!

      Sweeeet!! Thanks OWC. :)

    7. Travis Wright says:

      Will the 8500 1333DDR3 chips work in the 11,1 i7 iMac instead of the 1067mhz? Would there be any advantage to this at all?


    8. Harry says:

      How about iMac Core i3 Mid 2012?
      Core i5 and Core i7 models only?

      • OWC Michael says:

        This article is regarding the 2009 iMac models with model ID: iMac11,1 – not the latest 2012 models.

        That said, the iMac line didn’t include an Intel Core i3 option since 2011. So, which model were you meaning to refer to?

    9. Gilbert says:

      Can I just add the 8GB RAM in pairs? I currently have 4+4+2+2=12GB in my late 2009 i7 iMac. Can I replace my 2GB RAM so I have 4+4+8+8=24GB? Thanks.

      • OWC Michael says:


        • gianfranco pezzino says:

          Similar question about a mid-2010 iMac i7 (iMac11,3) – currently 4GB x 4 = 16 GB. Can I replace 2 chips and run 8+8+4+4 = 24 GB?

          • OWC Michael says:

            The iMac11,3 is OWC certified for up to 32GB of memory so 24GB would not be an issue.

            • gianfranco pezzino says:

              Thank you for your reply. When I upgraded my 27 inch iMac i7 from 8 to 16 GB using 4 x 4GB OWC memory modules, I encountered some problems of random, sudden reboot. After multiple attempts to find the cause, I swapped the OWC modules with Samsung modules, and the problem disappeared. That was, I believe, sometime in 2011. Do you know if I will run into the same issue if I upgrade to 8 GB OWC modules now? Also, if I only replace 2 of the 4 Samsung with 8GB OWC modules (for a total of 24GB), would there be a problem for the two brands working together? Thanks!

              • OWC Michael says:

                Really shouldn’t run into compatibility issues at all between different brands of memory. All OWC Memory is made to meet or exceed all Apple requirements for memory. A mis-seated or defective module can cause random reboots.

    10. Russ Tolman says:

      Any thing on the 2010, 11,3?

      That would be super


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