“Secret” Firmware lets Late ’08 MacBooks use 8GB.

Every once in a while, a blip on the radar comes up, letting us know that there’s something not quite right in our little corner of the Mac Universe. This time around, it came in the form of Tweets directed to us, as well as in posting in popular Mac forums.

As it turns out, several other memory vendors—along with some Late 08 MacBook/MacBook Pro users—have laid claim to these machines working with 8GB of RAM. This was contradictory to our testing in December 2009 which quite clearly showed that while these models recognized a full 8GB, if an application addressed more than 6GB, the system would slow down significantly.

Not being the type to just let these sorts of claims to go unchallenged, we went back to our testing lab, grabbed the affected model machines, running 10.6.6. and dropped an 8GB upgrade kit in them.

Related: See All Upgrades Compatible with Your Mac with My Upgrades Tool

The results were exactly the same as in 2009, lending credence to our conclusions, but the sheer number of claims to the contrary led us to continue searching—and the trail ended at Apple.

In late 2009, an EFI Firmware Update was released to address the buzzing noises coming from the optical drive. However, it seems that somewhere along the line, Apple changed this update without notating it anywhere.

Whether any other elements were affected by this change is undetermined, but it did change memory addressing; with the later version of the update installed, you could address a full 8GB in Snow Leopard. Unfortunately, Software Update doesn’t show this version as being different from the previous one, so users wouldn’t be notified if they had already updated their firmware to the older version.

The practical upshot of all this is that if you installed the EFI Update when it first came out, like we did, you would have gotten the old code, which meant your computer would only address 6GB properly. Those who didn’t upgrade until after Apple changed the updater got the newer firmware, which allowed proper addressing of 8GB.

Once we manually installed the “updated” version of the EFI Firmware in our test machines, they were able to address 8GB normally, without any crashing or slowdowns.

How do you ensure your Late ‘08 MacBook/MacBook Pro can address 8GB of RAM?

First, you want to make sure you have one of the affected models:

  • MacBook 13.3″ 2.0GHz and 2.4GHz
  • MacBook Pro 15″ 2.4GHz model w/ExpressCard Slot
  • MacBook Pro 15″ 2.53GHz model w/ExpressCard Slot
  • MacBook Pro 15″ 2.66GHz model w/ExpressCard Slot
  • MacBook Pro 15″ 2.8GHz model w/ExpressCard Slot
  • MacBook Pro 15″ 2.93GHz model w/ExpressCard Slot

Next, check the Boot ROM Version in your System Profiler.

  • MacBook Pros with a Model ID of MacBookPro5,1 should have a Boot ROM Version of MBP51.007E.B05. 
  • MacBooks with a Model ID of MacBook5,1 should have  a Boot ROM version of MB51.007D.B03
  • Machines with other Model IDs are not affected and don’t need an update.
  • **IMPORTANT NOTE: EFI Firmware Update 2.8 was released on February 28, 2012 for the Later 2008 MacBook Pro. If you have installed that update, your Boot ROM version will be MBP51.007E.B06. If you have this update installed, you’re already able to install the 8GB without any problems and don’t need to perform further updates to install more RAM.

If your Boot ROM version does not match the numbers above, download the appropriate firmware updater for your model machine and install according to the instructions:

Once you have ensured that the Boot ROM is the correct version, make sure your Operating System is updated to OSX 10.6.6. You must be running Snow Leopard or later to address 8GB on these systems, and our testing was done with 10.6.6, which is the earliest version we’re currently supporting for this.

Pardon us for our initial skepticism on this larger memory capacity finding. We had some pretty good reasons for it. First, this is the first time in our recollection that an EFI update and a dot version OS update both combined to affect memory addressing. Secondly, this reminded us of when after we were the first to qualify 2007-2009 Core 2 Duo MacBook Pro and MacBook models supporting 6GB max without experiencing a dramatic system slowdown, certain memory resellers pushed the same idea about 8GB compatibility.

Or in other shorter words, if we can’t prove either benchmark performance gains and/or system stability, we’re just not going to market a memory upgrade just to pad our MaxRAM credentials.

Your trust in us is more important than any other objective here.


Judging by the sheer number of comments, there seems to be some confusion as to which MacBooks and MacBook Pros this update applies to. We’ve created a simple flowchart that should help clear up some of the confusion.


EFI Firmware Update 2.8 was released on February 28, 2012 for the MacBook Pro, to resolve graphics issues. It does not disable the 8GB compatibility the previous firmware revision granted.

Related: Now is the time to upgrade your memory with OWC!


  • When OWC warrants supporting our memory in excess of the Apple factory supported amount of RAM, it will be listed on our OWC MaxRAM Memory Certification page. Please check that link if you are inquiring about additional machines not listed specifically in this post.

    One key factor to keep in mind is that OWC Brand memory meets or exceeds Apple’s specifications. As such, we are not stating that all brands of memory are included in this discovery, simply that OWC RAM has been newly tested and certified to work.

    That said, the links to both the compatible memory as well as the EFI updates can be found in the post. Most users will have already downloaded and updated to the latest version of the EFI Firmware prior to or along with the 10.6.6 update to OS X.

    If you want to make sure you’re at the latest firmware update, download the EFI updater for your specific MacBook/MacBook Pro listed in the post and run the downloaded updater. If you receive the message that the updater cannot be installed on your machine, then you are already at or above the required firmware update needed to install your 8GB of OWC brand memory.

  • Excuse my ignorance, but can anyone tell me which memory is suitable to populate the slots on my MBP? Unfortunately Crucial tells me I can only use 4GB :(

  • OWC Grant: “We don’t have a machine without the EFI update at this point now to know what the other Boot ROM versions were.”

    Strange that nobody has a machine with the first revision, the one before the “secret update”. And you just carelessly updated the machine without making a note of the old Boot ROM number?

    Something’s not right here. I updated my machine with the 1.8 EFI update, yet I have the revision that was supposedly the result of the secret update.

    It looks to me like either something went wrong with your testing right after the 1.8 update or the 10.6.6 update is the one that triggered the accessibility. But saying that Apple issued a “secret update” just doesn’t sound plausible to me.

  • I have a MacBook Pro 1.2 with two 1 g memory DIMMS, one in bank 0 and the other in bank 1. Is there a way to increase the RAM?

  • Can you please clarify if “MacBook Pro 15″ 2.4GHz (All)” also includes MacBookPro4,1 model (Intel Core 2 Duo 2.4 GHz)?


  • Has anyone compared the before and after differences?
    I’m assuming the update changes the boot.efi…
    I’d love to know where the differences are, as I’ve already got my MBP 3,1 booting 64-bit (with edited .efi) and have OWC 8GB DDR2 waiting :-)
    Any tips welcome!

  • I have boot ROM MBP31.0070.B07 on my 2.4 gHz Core 2 Duo MacBook Pro (2008). When I try to run the EFI updater from the OWC blog it states that my MBP does not need it. Given the other numbers (B03, B05) am I even further along in the EFI updates?

  • Hello.

    To sum up my actions.. I own a late 2008 MacBook Pro. Simply fired up a few VMware virtual machines and used them throughout the day. Also ran iometer to stress the SSD drive as well in the virtual machines. Memory went as low as 300 mb free. All I can say is that I did not experience any issues!

    For those if you with reservations, go for it. What have you got to lose, OWC has a 30 return policy (I think).


  • I have an early 2009 (late 2008) aluminum MacBook 13″. I run parallels 6 on it, and my RAM is maxed out when doing so. I do have an SSD, so it’s not the end of the world for me, but updating my RAM so I’m not maxing out is something I’ve been wishing I could do. I’m so glad that I can do it now! I’m taking the plunge!! I’ll let you know how it goes!

  • So @OWC is the manual update needed or will the automatic update from before work?

    Your blog says the manual update is required:
    “The practical upshot of all this is that if you installed the EFI Update when it first came out, like we did, you would have gotten the old code, which meant your computer would only address 6GB properly. Those who didn’t upgrade until after Apple changed the updater got the newer firmware, which allowed proper addressing of 8GB.

    Once we manually installed the “updated” version of the EFI Firmware in our test machines, they were able to address 8GB normally, without any crashing or slowdowns.”

    Reading that it indicates that because I did the automatic update that it will not work as I have the older info despite the correct version number.

    • Hi Orin:

      Need to clarify a few things here.

      First, we were able to update the firmware even though it did not show in the software update – but when we manually downloaded the EFI
      firmware update and tried it – it let us apply it. So that’s what’s meant by manually downloading and applying.
      Even though software update did not say it needed to be applied, it did obviously. And again, these machines certainly did not run with 8GB in our first tests – after the application of the firmware, they DO work with 8GB.

      And no, we unfortunately did not screenshot Apple System Profiler before and after.

      Should also perhaps clear up that the update is REQUIRED. Many users may find their firmware is already updated to the revision they
      need to run 8GB. So, besides 10.6.6, open up Apple System Profiler and examine the firmware revision – see what is installed
      – and if you actually need to take any action at all.

  • I have a late 2008 Macbook unibody and it shipped with Leopard and I never upgraded.

    Has anyone tried the 8GB max with Leopard (10.5.x) or is Snow Leopard (10.6.x) mandatory?

    • Hi Steve and thanks for stopping by. Yes…we tried with other “dot revisions”…the ONLY OS version we got the 8GB to work properly on was 10.6.6.

      Not sure what others will find…but that’s what we’re supporting as compatible…10.6.6 and the EFI version update.

  • Also, make sure to update your shopping cart information and receipt so that it confirms the Late 2008 MBP models are included. It is not visible anywhere once you begin checking out, confirming the order and getting the receipt. Thanks!

  • Thanks for posting this guys. You must have been reading my mind because I was thinking last week… “I wish I could boost the ram in my MacBook Pro!” Right now it only has 4gb total.

    So, I decided after reading the article on TUAW, then reading this blog to purchase the 8gb kit from OWC for my Late 2008 MacBook Pro 15″ 2.53 Core Duo model.

    *Fingers crossed* that everything works just fine when I install it tomorrow!

  • I’d also like to know if there is any chance that this would work for the 2008 iMacs. I’ve currently got 6GB in mine, when only 4GB is officially supported. Would love to have 8!

  • I have a late 2008 with 8GB from some time now, I had the EFI applied when apple told me to long time ago, but after the 8GB upgrade it crashes most of the time when coming out from hibernation and Programs like Illustrator and Photoshop where open (memory hungry programs).

    Beside that it works flawlessly.

  • Nice find guys! :) I have the same question as Chris (comment #19) though: if we’re certain that we have the older version of the EFI update, how can it be updated to the newer one?

  • Grant,

    It looks like I have one of these models and can do the upgrade.

    How would I test after the upgrade? Do you or Marvin have a step-by-step set of instructions? Do I just keep running apps until I see huge memory use? How can I exercise to prove that the dreaded slowdowns do not appear?



  • I bought the “4.0GB OWC PC8500 Module 204 pin w/6GB Model Qualification. Lifetime Warranty (OWC8566D6R3S4GB)” in late 2009 for my Macbook Pro which could only address 6Gb of memory at the time. My Macbook pro has the matching ROM version, so I’m just wondering if I can get the “4.0GB OWC PC8500 DDR3 SO DIMM 204pin 1066MHZ w/Lifetime Warranty (OWC8566DDR3S4GB)” to match my ram?

    Note that the model numbers are slightly different.


  • Order the 8GB kit on Saturday night, arrived Monday morning!! Works like a charm! Was a bit skeptical at first so ran a few tests that used over 7G of memory (rumors about the 6G memory limit scared me). Stable as can be!! Thank you OWC for the information.

  • I have MacbookPro late 2008, and I want to put 2x 4GB 1333Mhz.
    Do you think that will my MBP works nice with this 1333Mhz module (I know that will works on 1066Mhz), but I can’t find 2x4Gb 1066Mhz in my neighborhood.

  • I´m getting Kernel Panics with 8GB on my Macbook Pro 5.1 with the 1.8 Firmware.
    I tried to reinstall the firmware update, but it doesn´t let me saying ” its not need on this system”

    Please help, i really need 8GB :-)


  • What are the Boot ROM versions for the early EFI Firmware updated machines that didn’t get the memory addressing fix (those you had installed before re-testing)?
    Is it different from the ones mentioned above? I hope so, otherwise this post could mislead many.

  • There are mixed reports. Some with the affected MBP and the correct ROM are still reporting lock ups when addressing more than 6GB of RAM…

    This is a shame…

    How much testing has OWC actually done using more than 4GB/6GB on these machines…?

    I have the 2.53 Core2Duo model.


    • Hi Richard…yes…this was tested VERY thoroughly…in fact…early testing before we did the EFI updated and the 10.6.6 update got same results of significant system slow down over 6GB.
      We tested every 5,1 model ID MB/MBP with these updates applied and none had lockups, KP’s, slow downs, etc. We wouldn’t have reported on the successful results if they had ;-)

  • I understand that this article has been written as applicable to certain Macbook and MacbookPro models (the latter being what I have… and have now ordered the 8GB RAM upgrade kit). I was just wondering if any testing has been conducted on the late 2009 / early 2010 MacMini in regard to whether it would also have received a ‘secret’ Boot ROM update to allow it to take the 8GB upgrade. If so, I need to order another 8GB upgrade kit!

  • I have a white iMac of 2006 that is limited to 3GB max RAM. It has a core2Duo 2.33Ghz processor. I wonder if by updating it to the latest EFI firmware, I can get it to work with more RAM. Any thoughts?

  • Anybody had any luck doing trying this on the MBP 15″ 2.66 GHz models?

  • BTW, if these models could all along address 8GB of RAM and the only thing they needed was an updated firmware, then Apple incurred in a disservice to all of us who use their computers, I guess just for the sake of pushing their newer models.

  • This is good news, but several questions linger on:

    1. Will these 8GB of RAM work with Lion?
    2. Will Apple try to correct their “mistake” and release a new firmware to block the use of 8GB of RAM in the models listed in the article?
    3. Have you guys contacted Apple to confirm that they will allow the use of 8GB of RAM in the models listed?


    • Hi and thanks for your questions.

      As an Apple Developer, we are not allowed to discuss aspects of any unreleased Apple product.
      No idea what Apple will do current or future…unlikely though they would do a firmware updated just to block use of 8GB.
      No reason to contact Apple to discuss maximum memory….our MaxRAM program has been doing such verification for years now: http://eshop.macsales.com/memory/maxram

  • @m3kw: @A Bobyn’s question is a fair one, I think. I’m in the same position with my MP Pro of having the right firmware revision in System Profiler but not knowing if it’s the “right” firmware to expand the memory addressing.
    It seems clear in the post that there were two firmware updates, one of which enables the 8GB option without performance penalty and one which essentially brings no joy for us.
    With no way to find out which firmware revision I’m running, I’ve decided to pull the trigger on the second 4GB upgrade and just try it and see. I also get the “Does not need this update” message for the firmware update on a replacement motherboard that shipped in April 2009 from Apple.

  • Excellent news!i was about to upgrade my nieces 5,1 to 6gb. 8gb will be awesome.

    I do have a similar question to a previous comment… owc specifically mentions snow leopard 10.6.6. But what if we boot into bootcamp and windows? I suspect it will still work, correct? Would be nice to have extra RAM for running xp mode in windows 7 (virtual pc).

    Thanks for the awesome discovery!

  • You mentioned other model IDs do not require this update. Were you referring to models start with 5,* or could it apply to 4,1 models too?

  • What about my 2008 3.06 27″ iMac? It would be nice to give it a boost

  • Well, I took the plunge. Bought 2x4GB sticks today and put them in. Consumed 7+ GB of RAM, and none of the molasses-style performance. Great find OWC.

  • Excellent work OWC. All my Mac RAM has come from you, certainly a trustworthy source.

    Naturally of course I recently purchased 6GB for my late 2008 MBP 15 2.4GHz. Guess I’ll be using the RAM trade in program. I need 8GB for my late 2009 mini 2.66GHz so what the hell, time to buy more RAM!

  • I have all the required version numbers, when I try and install the firmware update I’m told this computer doesn’t require this update, exactly like the machine in the article. Since I’m diligent about updates, I’m sure I have the 6GB limit EFI. The authors of the article state:

    Once we manually installed the “updated” version of the EFI Firmware in our test machines, they were able to address 8GB normally, without any crashing or slowdowns.

    How do I *manually* install this firmware? I see the same question asked a few times and the response is always “You don’t need it”, but if this article is correct, then there are TWO versions of this firmware and while my MBP tells me I don’t need it, it’s quite likely I have the first version of this firmware and would need to overwrite it with the “new” firmware of the same version number.

    Advice anyone?

  • I have this system:
    Model Identifier: MacBookPro5,1
    Boot ROM Version: MBP51.007E.B05

    Do i need to flash with this?
    MacBook Pro EFI Firmware Update 1.8

    OR just to buy 2x4GB ram?


  • Hey guys,

    This is great news and more RAM sure comes handy. Would you suggest a RAM upgrade or a SSD one?

    I currently have an Unibody 15″ MBP (late 2008), 4GB RAM and 500GB Hybrid Drive.

  • I’m getting “Alert – This computer does not need this update.” while launching the Update 1.4 on my MacBook 13.3″ 2.0GHz with Boot ROM Version: MB51.007D.B03. No option to ignore and continue it just doesn’t let me run the package. Anyone with the same problem or a solution?

  • Very Good News!
    I am running Mac OS X Lion (Developer’s Preview)
    Is it going to work on me?I have the properly Boot ROM Version.

  • Wow, guys. Great find. This’ll be a cheap update to give my MacBook another year or more of life.

  • I wonder how this affects Windows 7 or Xp under boot camp?!?! Anyone?

  • So if I have a 2.13 Ghz MacBook (5,2) and have Boot ROM Version MB52.0088.B06, can I install 8 Gigs and have full use of it on my system running Snow Leopard??

  • @A Bobyn wow, please learn to read the blog properly, the version you have is the required version! MBP51.007E.B05 will work.

  • @David Lein If you have the required version MBP51.007E.B05 or MBP51.007D.B03 for model Macbook 5,1 you don’t need to update as it is already the version you need!

    Just install your 8 gig ram and BOOM. I just ordered mine when this news came out! I’m getting the G.SKILL 4GB DDR3 1066 (PC3 8500) Memory for Apple Model FA-8500CL7S-4GBSQ

    I hope it pairs up with the 4gig i already have it’s the F3-8500CL7S-4GBSQ. The difference is FA and F3 in the model numbers.

  • So, meeting all the requirements listed with the OS version, model MacBook Pro, and boot ROM version, I get a fail when I try to apply the “new” version–“This computer does not need this update”, and can only close. What am I doing wrong?

  • What if your Macbook is running a later version of the boot ROM? ie:

    has a Model ID of MacBook5,1
    has a Boot ROM version of MBP51.007E.B05 (not MB51.007D.B03)
    is running Mac OS X 10.6.6 or later

    will it still be able to address the full 8GB?, or would one need to downgrade (if possible) Boot ROM to MB51.007D.B03?

  • This is a remarkable development and all but demands some more research and details for those of us who aren’t quite ready to upgrade.
    I’ve got a BTO 2.8 ghz model that had its motherboard replaced in May 2009. It’s never been able to accept that update, so I suspect that Apple may have sent an upgraded motherboard as a replacement.
    8GB is important enough to me for me to consider pulling the trigger on the upgrade anyway, but I’m wondering if it’s likely to work.

  • So if I have a MacBook5,1 with the boot ROM version mentionned above, I CAN buy your 8 GB upgrade kit?

    • If your MacBook:

      • has a Model ID of MacBook5,1
      • has a Boot ROM version of MB51.007D.B03
      • is running Mac OS X 10.6.6 or later

      you should be able to address the full 8GB

      • And to extend this explanation…..you can address that 8GB and enjoy full system performance without the previously found significant system slow down 8GB presented before this EFI update. That’s why up until today, we only supported 6GB for these models.

  • I see my 2008 17″ MacBook Pro is conspicuously absent. Any chance there is a similar update for it?

    • This particular issue affects only the models listed.

      While it wouldn’t be a bad idea to make sure you have the latest EFI Firmware installed, for compatibility’s sake, it is doubtful that it’s going to make the kind of change we’ve seen here.

      You can find the latest version of this firmware at the “Check Boot ROM version” link above – lower on the page is a list of the latest versions each model can take.

  • Very good to know. Hopefully the new 2011 MBPs get a similar update for 16GB when the 8GB DIMMS are more widely available. :)