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Jeff Mark Level 1 Level 1 (5 points)



Please see here for reference. Apparently I am able to load two 2GB modules in my MacBook despite the original specs, which said 2GB total max.


So, can I do similarly on my '08 iMac, currently maxed out at 4GB? I.e., cram two 4GB modules into it? If it turns out the system can only address 6GB-7GB of that (as with the MacBook), that's OK. Turns out Mt. Lion is heavier lifting than this thing's used to. (I've considered a drive upgrade but that would require professional help. RAM I can do myself.)


Processor  2.8 GHz Intel Core 2 Duo


Memory  4 GB 800 MHz DDR2 SDRAM


On the other hand, I did some looking around and it would appear that DDR2 PC2-6400 is not available larger than 2GB. Would some other format do as well?


Thanx muchly,




P.S., I eagerly await the next release of iMacs, whenever that might actually happen...

iMac (24-inch Early 2008), OS X Mountain Lion
  • RRFS Level 5 Level 5 (4,490 points)

    go to Crucial or OWC they will recommend the proper amount of RAM for your system. I have 6GB in my one 2GB and one 4GB, works great. Be careful as Macs are very particular about their RAM, even some that meet specs won't work properly.

  • MichelPM Level 6 Level 6 (10,235 points)

    The max RAM you can install into your iMac is 6 GBs.

    No more than this.


    Here's the specs for you RAM.


    6.0 GB (Actual) 4.0 GB (Apple)

    Memory Slots     2 - 200-pin PC2-6400 (800MHz) DDR2 SO-DIMM


    You can buy reliable RAM online from Crucial memory or OWC.

  • Jeff Mark Level 1 Level 1 (5 points)

    Thanks. Please see my update tho. (I agree about Crucial, I recently bought a SSD for that MacBook and they were very helpful. But would they receommend spmething that excceeded mfr specs? But thanks for the suggestion.)

  • RRFS Level 5 Level 5 (4,490 points)

    No, because they want their guaranteed products to work properly.

  • MichelPM Level 6 Level 6 (10,235 points)


    Your iMac is not capable of addressing more RAM than the 6 GB limit.


  • Jeff Mark Level 1 Level 1 (5 points)

    Hi Michel,


    I'm missing something in your response, please let me try again. If I could put 8GB into my iMac but only access 6GB, that would be OK. That's similar to the situation with my MacBook.


    I have two slots. Currently they both contain a 2GB DIMM. If I understand what you and RRFS are telling me, if I could get 8GB (say, two 4GB DIMMs) into it, I could address about 6GB of that, which, as I said would be an improvement.


    The issue would seem to be finding actual 200-pin PC2-6400 (800MHz) DDR2 SO-DIMM in a 4GB size. Crucial didn't seem to carry any, but OWC has a 6GB kit (!). Little pricey, tho. Also, I thought iMac RAM had to be in matched paiurs. Maybe not.


    Thanks, have some points.

  • RRFS Level 5 Level 5 (4,490 points)

    When I got my 6GB of RAM I tried putting the 4GB module in the fist slot, it was not recognized, so that would be a no to the 8GB question.

  • Jeff Mark Level 1 Level 1 (5 points)

    You might have an opportunity ro teach me something here. As I said above, I was under the impression that RAM had to be installed in pairs. I guess not. So, are you and Michel telling me that I could replace one of my 2GB modules with a 4GB module (as apparently available from OWC), and get to use all 6GB, but it has to go in the #2 slot?


    Is that right? How bizarre. Was it just not there in #1 (i.e., "0GB"), or did the system refuse to start? Do you understand what that was about, and can you explain it briefly in terms understandable by one such as myself?

  • RRFS Level 5 Level 5 (4,490 points)

    It gave me 3 beeps and refused to start. I'm not sure if the "pair" of modules I got from Crucial is matched somehow or maybe it's tested by them to know it works together. I only know it was at least the same specs just 4GB instead of 2GB.

  • Jeff Mark Level 1 Level 1 (5 points)

    But it was OK when you put the 4GB in #2? And the system saw all 6GB?

  • MichelPM Level 6 Level 6 (10,235 points)

    Yes, when applicable, it's always better to install RAM into an iMac in pairs.

    But for the iMsc models that take the 6 GBs of RAM, putting (2) 4 GB RAM pairs does not work in these Macs.

    I believe it's OWC that tests how much max RAM can be installed in Macs.

    Not all Mac models can exceed Apple's stated max. RAM amounts.

    Those that do exceed Apple's stated amount can vary widely in their amount of max. RAM.

    For the 2008 models the only combination that was found to work is to install a 2 GB, than a 4 GB stick into these Macs for a total of 6 GBs.

  • MichelPM Level 6 Level 6 (10,235 points)

    Yes, That would be the correct order for the RAM.

  • Jeff Mark Level 1 Level 1 (5 points)

    Let me complicate this just a bit more.


    My iMac has one 2GB PC2-6400 DDR2 800MHz SO-DIMM 200 Pin that I will be removing. My MacBook takes PC2-5300 DDR2 667MHz SO-DIMM 200 Pin.


    Would the former be likely to work in my MacBook (meaning one fewer PC2-5300 DDR2 667MHz — or PC2-6400 DDR2 800M, maybe — that I have to buy)?


    In fact, let's say I got one of OWC's 6GB kits for the iMac, could I just move those into the MacBook? That would save a few $$.

  • RRFS Level 5 Level 5 (4,490 points)

    Doubt it would work. I wouldn't take the chance of it damaging some other component like the motherboard if it has a different pin configuration (for some inexplicable reason).

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