“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.

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.

UPDATE – FURTHER CLARIFICATION

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.

UPDATE: FEBRUARY 2012

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.


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  • Hello,

    I am looking for some feedback on issues I am experiencing with my late 2008 aluminum unibody Macbook. Here are the specs:
    Model ID: Mackbook 5,1
    OS: 10.10.1 (Yosemite)
    Processor: 2.4 GHz Intel Core 2 Duo
    Memory (stock): 2 GB 1067 MHz DDR3
    *Memory (current): 8 GB 1033 MHz DDR3
    Graphics: NVIDIA GeForce 9400M 256 MB
    Boot ROM Version: MB51.007D.B03

    I am experiencing sporadic Kernel panics after upgrading the RAM to 8 GB (2×4 GB). My boot ROM version is correct, thus I do not think I need the firmware update. Machine runs iTunes and iPhoto much faster than it did with stock 2 GB RAM, but now goes into Kernel panic either out-of-the-blue, when I try to come out of screensaver mode, or when I am using Chrome while iTunes is downloading/updating.

    Any advice on this issue or ideas on what’s going wrong are highly appreciated!




    • Hi, I just checked my MacBook and it has 2x4gb 1067mhz DDR3 fitted… I hope the issue is not caused because yours is only 1033mhz… :(




      • Bus speed on my machine is 1.07 GHz. The RAM I purchased claims to be 1066 MHz compatible. This is actually the second set of 4 GB sticks I’ve tried. Exchanged the first set after determining them to be faulty. These ones have worked a lot better so far, it just seems like the machine gets overworked and Kernel panics.

        Hoping the issue isn’t just from buying cheaper RAM :(




    • Bus speed in system report shows 1.07ghz btw… don’t know if this matters though…




    • Sorry for the multi-episode answer, but I’m 99% sure your ram is too slow… Found this on everymac.com : RAM Type: PC3-8500 DDR3 Min. RAM Speed: 1066 MHz
      Details: Supports 1066 MHz PC3-8500 DDR3 SDRAM.

      link: http://www.everymac.com/systems/apple/macbook/specs/macbook-core-2-duo-2.4-aluminum-13-late-2008-unibody-specs.html




    • I’m sorry to hear about the issues. It sounds like you may have bought 1333MHz RAM instead of the proper 1066MHz RAM. If that is the case you’ll want to exchange them for the proper 1066MHz RAM.

      If you do have 1066MHz modules, I recommend trying to clean the memory module. Take a clean pencil eraser and gently rub it along the metal contacts on the memory and follow that by using a microfiber towel along with rubbing alcohol to clean the metal contacts on the memory, this should insure that the memory is getting a solid contact with the computer

      If that doesn’t resolve the issue, I would try both and SMC and PRAM reset.

      SMC reset: http://support.apple.com/kb/HT1411

      And

      PRAM Reset:
      1) Start the machine while holding down the Option-Apple-P-R keys

      2) Wait until you hear the 3rd startup chime, then let go of the keys and let the machine boot up.

      Lastly if the issue is still unresolved, I recommend running an application called Rember. Rember is a free download at http://kelleycomputing.net:16080/rember/. Once you have it downloaded please run a 3 pass test. This application will let us know if any issues are present on the memory modules.