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Putting a rumor to rest – OWC supports 6GB MAX in Late 2008 MacBook Pro

Apple released MacBook Pro EFI Firmware Update 1.8 on December 8th, 2009, sparking a new interest in the Late 2008 MacBook Pro models and their maximum memory capacity.

Apple supports up to 4GB of memory in these machines, but OWC has done the testing with our memory modules and has been able to support 6GB of memory since their release. However, there was something interesting we found with our testing when trying to qualify the laptops to accept 8GB of memory. Simply put, while System Profiler recognized that there was indeed 8GB of memory installed, once more than 6GB of memory was actually put to use, the performance of the overall machine diminished.

Of course, when we heard the rumors circulating again that the Firmware Update may have silently addressed this issue as well, we got excited and performed the qualification testing again after installing the update. Unfortunately we found the same scenario on all the machines. The machines were faster the more memory we installed until more than 6GB was present. Once the machine tried to address the final 2GB of memory the performance started to suffer yet again.

It would have been nice to officially support twice the memory that Apple intended, but alas, we’ll have to settle for a 50% increase. Which all in all – isn’t bad.

The machines that were rumored to go to 8GB, are supported to only 4GB by Apple, and have been tested and confirmed by us to 6GB are:

  • MacBook Pro 15″ 2.4GHz (All)
  • MacBook Pro 15″ 2.53GHz model w/ExpressCard Slot (Late 2008)
  • MacBook Pro 15″ 2.8GHz model w/ExpressCard Slot (Late 2008)
  • MacBook 13.3″ 2.0GHz (All)
  • MacBook 13.3″ 2.4GHz (All)
  • White MacBook 13.3″ Intel Core 2 Duo 2.13GHz
  • The Story Continues… “Secret” Firmware lets Late ’08 MacBooks use 8GB.

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    • I’m trying to get a Late 2008 Aluminum Unibody MacBook 5,1 2 GHz back up and running. Haven’t used it in a while, and it is very slow. Want to just be able to use it for iMovie, Google, email etc. Would you recommend I upgrade just one chip to 5GB total, or both chips to 6 GB total?

      • Thank you for asking! We would recommend upgrading to 6GBs of RAM. This will provide the best performance in your machine.

        You can also look at upgrading the internal drive to a SSD!

        • Could you please provide a link to the correct chips(2GB & 4GB) and also a separate link to the SSD you recommend? Thanks!

    • I have 2 Macs one is a regular MacBook early 2008 the other is a MacBook Pro 15″also an early 2008. I want to update my ram in both computers. So I want to know if I the ram out of my MacBook Pro & put it into the the regular MacBook? If so then I would only have to buy a 4 GB ram for my MacBook Pro

    • HI guys. So i have a macbook pro a1226. No hard drive and no ram. I produce music and I want the best hd and ram in it. Can I put a solid state drive in there along with 8gb of ram?

      • Hello Thomas. You can use a SSD in your computer, however it is good to note the SATA interface is SATA I 1.5G. So a SSD will still give you good performance but it will not be as monumental as the later model computers with SATA II and SATA III interfaces.

        The Maximum allowed memory is 6Gb, 8GB will not work in your computer. You can find the 6GB kit here

    • Hi. I have an Early 2009 MacBook – MacBook 5,2

      I currently have 2x1GB in it.

      Officially it handles 4GB. Unofficially it handles 6GB.

      Can this handle 2x4GB without any problems.


      • The Early 2009 MacBooks can accept up to 6GB of memory. For the 2.0GHz model see here or for the 2.13GHz model see here as they take different types of memory – but nether will accept 2x4GB.

    • By upgrading to 6GB of memory, are there any risks to the logic board? I had a tech at a certified dealer tell me that it could “hurt the computer.” I know that programs may crash and software might fail, but I (currently) don’t see how it could fry a logic board or other parts of the computer. The minimal extra power draw should be within tolerance of good design principles. Or am I missing something?

      • No, you can install with confidence. Our MaxRAM Certification Program accounts for power draw and other host machine tolerances as well as performance testing.

    • ok, i’m still having trouble understanding all of this.

      i have a late 2008 mbp 5,1, but the 2.4ghz version (so october 2008, not march 2009). can i use 8GB?

    • So, now when your site indicates that a late 2008 Macbook supports 8GB, 6GB is really what it supports? If so, why are you selling 8GB upgrade kits for this machine?

    • note to OWC staff: it would be nice if you DATE STAMPED the replies/comments. It’s hard to tell if comments are from recently, or from a year ago. :-)

    • Hi Grant,

      I understand that you guys have done extensive testing for the Macbook5,1 6gb ram compatibility. But i just want to know, since it is fine to do a 4+2 = 6gb of ram, why is it Apple recommends both slots to be equal amount of memory modules?

      • Apple suggests this due to the dual channel memory bus. If each channel has equal amounts of RAM, then the RAM can be accessed simultaneously, creating better speed of performance due to faster access to the RAM. However, from our testing, we’ve found that more memory capacity itself just about always outperforms having a smaller amount of memory installed in pairs. This is evident in our memory benchmark testing located here: (The MacBook 5,1 is shown in green on the charts)

    • Hi Grant,

      Thanks for the prompt response. I checked and you are correct it is the MacBook Pro 5,1.

      I’m slightly nervous about adding the 4GB RAM as I have read of people having trouble but if you guys are certain it’ll work with one 2GB module of my existing Apple-supplied RAM then I’ll go ahead with the order :-)



    • Hi,

      I have a 2008 2.8ghz Unibody MBP running 10.6.3. I want to upgrade to 6GB memory. I currently have 4GB of Apple-Supplied memory. Will I be able to order just a 4GB module? From a previous poster this would seem to be the case. To be sure I’m ordering the right one, can you post a link?

      Also, any ideas for what I’d get on sending you my old 2GB module?



      • NP…it’s what we’re all here for. I’d say it like Telly S. used to…but while I share his clean headed looks…I should come up with my own “love” line.

    • I realize this is an old post, but I am trying to figure out if my mac will take the 6Gb. When I use the “My OWC” tab and browse to my computer a Macbook Pro 15″ 3,1 2.2 Ghz it leads me to a page with the 6Gb pair. (I already have 4Gb, so would only buy the single 4Gb chip.) But I do not see my computer listed in your list in this blog post. Model # A1226, which I blieve is a “Santa Rosa”. Not sure on the time period.

      • Hello Jennifer…believe your machine is on this page:
        And believe you have 2 x 2GB for a total of 4GB…
        since the machine can be maxed out at 6GB…you would want the single 4GB module to add to one of the 2GB chips you have. Then you can either send in the remaining 2GB module for a cash back rebate or hang on to it in case your other 2GB module ever goes bad.

    • OWC folks,

      2 memory questions about my 2.53 MB471LL/A (late 2008) currently running 4 GB RAM:

      1. Can I just order your 4 GB memory and use one of my existing 2.0 GB modules to make the 6 GB?

      2. Does it matter which bank is which, and if so, does the memory come with instructions?

      Thank you,


      • Hello Dave,

        You certainly could add a 4GB memory module to the existing 2GB module to total 6GB of memory in your Apple MacBook Pro 15″ (Late 2008 “Unibody”) machine.

        The machine will perform the same whether the 4GB chip is in the top bank or the bottom bank.

        If further instructions are desired, we do offer our line of installation videos here.

    • Thank you OWC Michael.

      so… it looks like I have a MacBook Pro 15″ (Late 2008) released March 2009 (so confusing. Apple should find a better way..).

      Based on that, I will give 8GB a try…

    • OWC Michael,

      I am a little bit confused with your post listing the Models.

      I have a Late 2008 MBP 15″. At least I think it is a Late 2008 MBP 15″. It is 2.66GHz, Model Identifier says: MacBookPro5,1 and it has the ExpressCard slot.

      In your post, you say that MacBookPro5,1 go up to 6GB ram but in the list of models you say that all 2.66GHz models support 8GB ram. Does my model supports 8GB Ram?


      • Sorry for the confusion, I can see where my phrasing in my comment from 12/23 could be misleading. I should have listed it as “It is only the MacBook5,1 model identifier machines listed specifically below that we are referring to being limited to 6GB.” There are MacBook5,1 models that can go to 8GB.

        As far as the MacBook5,1 models go – The three models released in October 2008, OWC supports to 6GB of RAM:
        MacBook Pro 15″ 2.4GHz
        MacBook Pro 15″ 2.53GHz model w/ExpressCard Slot (Late 2008)
        MacBook Pro 15″ 2.8GHz model w/ExpressCard Slot (Late 2008)

        The two models released March of 2009, OWC and Apple support up to 8GB of memory.
        MacBook Pro 15″ 2.66GHz (All)
        MacBook Pro 15″ 2.93GHz (All)

        I hope this clears that up for you.

    • OWC Michael, did you experience kernel panics with 6GB on the macbook5,1 on snow leopard prior to the december 8 update or not?

      All threads I followed prior to this period (between release of snow leopard and december 8) had indications of users experiencing kernel panic on the macbook5,1.

    • I have the macbook5,1 2.4Ghz, 4GB RAM. I read that after snow leopard, owners of this machine were experiencing kernel panics when using 6GB of RAM.

      Am I understanding this correctly, that after the snow leopard update of December 8th, 2009, the macbook5,1 will support 6GB of RAM without frequent kernel panics?

      • We haven’t run into any issues with the RAM we state as compatible. Our MaxRAM in-house testing of these modules is quite extensive, however, we do not test every brand and manufacturer of memory. OWC does support our 6GB memory set in these machines to work flawlessly (no frequent kernal panics, system freezes, etc.) in the MacBook5,1 model identifier machines.

      • Yes, Apple does sell 8GB of memory for their current line of MacBook Pro machines and so does OWC. To try to alleviate some of the confusion, here is a full listing of the models. It is only the MacBook5,1 model identifier machines that we are referring to being limited to 6GB. Later revisions can certainly go up to 8GB of memory as indicated by Apple.

        MacBook Pro ‘Unibody’ Models OWC tested to support Maximum Memory of 8.0GB:
        MacBook Pro 13.3″ 2.26GHz (All)
        MacBook Pro 13.3″ 2.53GHz (All)
        MacBook Pro 15″ 2.53GHz model w/SD Card Slot (June 2009)
        MacBook Pro 15″ 2.66GHz (All)
        MacBook Pro 15″ 2.80GHz model w/SD Card Slot (June 2009)
        MacBook Pro 15″ 2.93GHz (All)
        MacBook Pro 15″ 3.0GHz (All)
        MacBook Pro 17″ 2.66GHz (All)
        MacBook Pro 17″ 2.93GHz (All)
        MacBook Pro 17″ 3.06GHz (All)

        MacBook and MacBook Pro ‘Unibody’ Models OWC tested to support Maximum Memory of 6.0GB (Apple supports up to 4.0GB of memory in these models):
        MacBook 13.3″ 2.0GHz (All)
        MacBook 13.3″ 2.4GHz (All)
        MacBook Pro 15″ 2.4GHz (All)
        MacBook Pro 15″ 2.53GHz model w/ExpressCard Slot (Late 2008)
        MacBook Pro 15″ 2.8GHz model w/ExpressCard Slot (Late 2008)

    • Can you try the following please?

      Put 2 x 4GB memory modules in a Late 2008 MBP and then reboot with an edited version of /Library/Preferences/SystemConfiguration/ Make it look similar to the following:

      Kernel Flags

      Can you let us know if it’s stable and if so, maybe increase it to 7 GB? I’d be interested to know if I could retain the benefits of having 2 identical RAM modules in the machine even if I could only make use of 6 GB of RAM vs 8 GB. Thanks!

      • Hi Paul:

        Unfortunately, performing any type of system hack and publishing the results of such to facilitate the sale of a third party product would violate Apple Developer Connection terms.

    • Michael, does that mean your are not at liberty to say whether you have tested the machines using the 64-Bit kernel? It seems you are not willing to comment on that. Not exactly what I would consider “putting a rumor to rest”.

      • Hi Peter…since OWC Michael is out with an emergency, I wanted to jump into fray so weekend doesn’t go by and no reply.

        I gotta go back to the original statement in the post:

        “However, there was something interesting we found with our testing when trying to qualify the laptops to accept 8GB of memory. Simply put, while System Profiler recognized that there was indeed 8GB of memory installed, once more than 6GB of memory was actually put to use, the performance of the overall machine diminished.”

        Thus, the 8GB rumor, at least from our perspective and what we feel we should offer to our customers, has been put to rest…lol…at least for now.

        Hey…that’s why you keep coming back, right? If and when we find out anything new with any machine, we’ll try to be the first…esp when it comes to memory…to let you know.

        Thanks as always for your interest and community building here!

      • Hello Peter,

        Both the 64-bit and 32-bit kernals are tested. We encountered no difference between the two when exceeding 6GB of memory in these machines.

    • How can I reproduce your result? I installed 8GB memory in my MacBook Pro Late 2008 2.8GHz with EFI 1.8. Everything goes well, no slowdown occurs even if wired + active memory exceeds 6GB. I tested with Snow Leopard 10.6.2 32/64bit kernel modes and Leopard 10.5.8.

      • Hello Echo,

        Our MaxRAM Certification Tests are proprietary and used to determine what Other World Computing memory modules we are willing to support in a specific machine. Of course, there are those people out there that will tweak their systems to give the best performance for them, and if exceeding the OWC MaxRAM supported amount of memory is working for you, then that’s great – but OWC only supports memory which has proven to provide maximum system performance with a variety of applications with no degradation of either sytem or application performance.

    • @OWC Larry: Have you actually tested the first generation MBPs with Snow Leopard’s 64-bit kernel or you just assuming?

    • The same applies to the 2008 iMacs which use DDR2 PC6400 memory. 6GB is the max that is usable… will show 8GB when 2 x 4GB installed, but once 6GB of in use memory is exceeded – system slows to a crawl as is the case for all the 6GB max models.

    • Thanks for testing this, it’s really helpful.

      I would be really interested to know if things changed when using the 64bit kernel under snow leopard. Apparently this possibly makes a difference.

    • Hi Michael,

      Thanks for testing that. I was just wondering whether you have also tested the late 2008 MBPs using Snow Leopard’s 64-Bit kernel mode. A few users claim to have not had the sluggishness you refer to after 6GB are addressed when running the late 2008 MBPs in 64-Bit kernel mode.

    • Does similar test were applied to 2008 AL iMac (24″ 2.8 GHz Intel Core 2 Duo) that are also being presented as 6GB capable? If so, how well the machine perform with both unsupported upgrades?.

      Juan Cruz

      • Hello Juan,
        Absolutely! We test each machine though our MaxRAM memory qualification program to see how much OWC memory each will support. When OWC stands behind an amount of memory greater than the Apple specified maximum for a particular model, you can rest assured it has been fully tested and backed by the OWC memory warranty.

    • Concerning the express card slot on the 17″: yes indeed, this together with screen size is a definite advantage; still waiting though for the Snow Leopard compatible Express Card driver, from Apiotek/Silicon Image, presently in beta, final version announced any time soon, and none to soon!.

    • Hello!
      Very informative blog! Well I have a couple of questions about this topic. You mentioned that 8gb were addressable, however, once the computer tries to use more than 6gb, you specified that the computer diminished its performance. The question here is: Did you guys need to force a shut down, or simply the machine just went slower?
      The other question that I have is about buying either the 4gb stick or the 6gb (4gb+2gb), I currently have my computer with 4gb ( I find it enough for my needs…yet) However, I want some guidance. Is it better getting the 6gb kit or just replace one of the 2gb sticks with the one of 4gb?
      thanks a lot!

      • The machine went noticeably slower but no forced shutdown was necessary. As far as adding additional memory to your system, there’s no need to buy a 2GB module to replace a 2GB module already present. Save yourself the cash and purchase just the 4GB module.

    • I’m happily running 6GB (4+2) on a late 2008 Unibody MB. I’m also running a 64-bit 10.6.2 kernel with the boot-efi “hack” with no apparent issues beyond a few devices not having 64-bit drivers (USB Ethernet for instance). I was wondering if anyone’s tested if the 64-bit kernel makes a difference on the memory limit, or is it a hardware limit?

      I’d be happy to test a second 4GB module if someone wants to loan me one? :-)

      BTW I find the 64-bit kernel and the maximum RAM useful as I frequently need to run Virtual Machines, not because I can. ;-)


    • One benefit that does remain with the 17″ is the presence of the ExpressCard Slot. The 15″ lost that with the June ‘update’ and is a real bummer given the eSATA, FireWire, and variety of other performance expansion options that this slot supports.

      To summarize 8GB vs. 6GB:
      All Apple MacBook Pro 15″ and MacBook 13″ models shipping in 2008 were Apple Factory listed for up to 4GB and are OWC ‘MAXRam’ Certified for up to 6GB. This includes pre-Unibody models as well…

      All Apple MacBook Pro 2.4GHz 15″ Unibody Models, including the 2.4GHz shipping in March/2009 until was replaced in June/2009, are 6GB limited. All MacBook 13″ Unibody Models shipping as current model until they were replaced with the ‘Pro’ model in June are 6GB limited.

      All Apple MacBook Pro 15″ 2.66GHz and 2.93GHz models with ExpressCard (started shipping in March/2009) are 100% A-OK for 8GB – ‘OWC MAXRam’ certified – although Apple lists only to 4GB.

      All Apple MacBook Pro 17″ unibody models are Apple spec for up to 8gb and always been A-oK for up to 8GB.

      All Apple MacBook Pro 13″ and 15″ models shipped since June/2009 (SD Memory Slot equipped, no Expresscard slot) are Apple Spec for up to 8GB and always benn A-OK to 8GB.

      The new ‘White Unibody’ 13″ MacBook Model, introduced in October/2009 (White-Plastic-No FireWire 400 Port) is Apple listed for only 4GB, by 100% A-OK ‘OWC MAXRam’ Certified for up to 8GB.

      I think i covered them all….

      As a side note, back in March Apple only listed the Mac Pro 4-Core as supporting up to 8GB. We very early on ‘MAXRam Certified’ the 4-cores for up to 16GB no problem. Nothing has changed hardware wise or otherwise… but with the introduction of the Mac Pro 3.33GHz 4-Core processor option a couple days ago, they quietly changed to note support up to 16GB for all the processor speed options.

      What I am getting at… some of the limitations are truly related to hardware. Some may be more about marketing… Either way – we’ve got nearly every Mac every made and all the processor variations of the the recent included. You can count on us to set it out there straight for what’s what for memory options. :)

    • Thankyou Michael, I note that rewiews for 17″ will be coming soon; good news. From the length of the present list, it looks like 15″ models are The more popular ;-)

      • Not only are the 15″ models more popular, but from past benchmarking, the screen size made very little difference, if any, in the performance. So if you match up the processor in the 15″ with a comparable 17″ model, the benchmark results will be very close if not identical.

    • The Apple store proposes 8GB as an option on the present 15″ & 17″ models. Have you been able to verify performance on these latest models, or can we confidently take it they will gainfully deploy the full potential, that is faster, right through the 8GB?