The following guide provides step by step instructions on how you can upgrade RAM memory on your Apple iMac 20", iMac 24" aluminum (2007, 2008 and early 2009 models) and also on iMac 21.5", iMac 27" (late 2009, 2010 and 2011 models) - and increase your computer's performance.

Article revisions: Jan, May, Oct, 2008.

Jan, Mar, Apr, July, Sep, Dec, 2009.

Disclaimer

Although chances for you damaging your iMac while upgrading RAM memory are astronomically small, please note that we cannot be responsible for any damages or losses you'll potentially incur from following this guide - thank you for your understanding! :)

Upgrade memory (RAM) on your iMac 20", 24" (2007, 2008, early 2009) and iMac 21.5", 27" Aluminum (late 2009, 2010, 2011)

Copyright 2007-2011 Amfiteatar Portal. All rights reserved.

What You'll Need

1) Precision screwdrivers

Six-Piece Mini Torx Screwdriver Set

2) RAM Memory

Your iMac (models 2007, 2008 and early 2009) has two memory bays (slots) available.

Your iMac (models late 2009, 2010, 2011) has four memory bays (slots) available.

First, you need to determine how much memory you already have installed and if one, or all memory bays are being used. You can identify this by clicking on the Apple logo (upper left corner), then by clicking on About This Mac.

in About This Mac window you can find out how much memory do you have installed in total, however we also need to know if only one or both memory bays have been used. In order to find this out, click on More Info button at the bottom of the window.

Selection of more info will display System Profiler window - in there click on the Memory menu option on the left hand side and you'll be able to see the capacity of individual memory sticks installed in your machine and if one or both memory bays are occupied.

iMac 2007 screen shot shows 667Mhz memory modules installed:

iMac 2009 screen shot shows 1066Mhz memory modules installed:

Memory Upgrade Options (iMac 2007, 2008, early 2009 - all 20" and 24" models)

(for late 2009, 2010 and 2011 models 21.5" and 27", please scroll down)

Depending on how much memory do you already have and which memory bays are used provides you with a number of upgrade options. For easy communication we've made the following table for your reference:

If only one of your memory bays is used, you can choose an option to add another module in there, or completely discard the existing module installed and install two new ones. Several examples on how this can work out in your case:

• if both of your memory bays have 1 GB memory modules installed (total of 2GB), in order to upgrade to 4GB, you will need to discard both of 1GB modules and install two new 2GB modules
• if you only have a single memory module installed, let's say 2GB, you might add another 2GB module in unoccupied bay in order to get to 4GB. (2 modules of 2GB = 4GB)
• maximum configuration for iMac 2007 and 2008 models is 6GB, in such case you need to use 2 memory modules - one 2GB and the other 4GB (1 module 2GB and 1 module 4GB = 6GB)
• similarly, maximum configuration for iMac2009 model is 8GB, in such case you need to use 2 memory modules - both 4 GB (2 modules 4GB = 8GB)

If you need to discard your old memory module in order to free up a memory bay, you can always consider giving it to a friend, or selling on eBay.

(for choice of recommended memory modules, please scroll down)

Memory Upgrade Options (iMac late 2009, 2010, 2011 - all 21.5" and 27" models)

Newer Mac models (late 2009, 2010 and 2011) have four (4) memory bays (slots) available (unlike their predecessor having only 2 memory bays). Depending on how many memory slots you have used, there are quite a few combinations in terms of possible upgrades. Please reference the table above in order to determine your upgrade options and memory modules you need to add, or to replace. The highest capacity these machines can be upgraded to is 16GB of RAM - all four (4) memory bays (slots) populated with 4GB 1333Mhz PC-10600 SODIMM memory modules.

(for choice of recommended memory modules, please scroll down)

Choosing the appropriate memory modules for iMac 2007, 2008, 2009, 2010 and 2011

Did you know that all iMac models use laptop (and not desktop) type of memory modules (they're called SO-DIMM memory modules)? That same memory does not have to be Apple branded, and it is also used in PCs as well - the same exact memory chips, the same exact components. Having said that, there are quite of few inexpensive options for upgrading your iMac memory on the market.

- iMac 2007 - (20" and 24")

The appropriate memory modules going into iMac 20" and iMac 24" aluminum 2007 models are the following PC2-5300 modules (1 GB or 2 GB modules, DDR2, 667 MHz, SO-DIMM 200 pin, unbuffered):

RAM for iMac 20in, 24in 2007 models		2 GB module (667 Mhz)	4 GB kit (2x2GB) (667 Mhz)	4 GB single module (667 Mhz)
		For 6 GB upgrade use one 2GB 667 Mhz module and one 4GB 667 Mhz module.

Althoug offical Apple specifications say that this model can be upgraded to 4 GB RAM in total, it is a well known fact in the Mac community that iMac 2007 can be upgraded to 6GB RAM in total (because it has the same Santa Rosa chipset used in iMacs supporting 8GB of RAM). Some Mac users have tried upgrading this model to 8 GB RAM, however it proved to be very unstable and the hardware just couldn't handle it. Upgrading to 6 GB is stable and works very well in these models.

In order to max out your iMac 2007 memory to 6 GB you will need one 2GB 667Mhz unbuffered so-dimm and one 4GB 667Mhz unbuffered so-dimm memory module complying to PC2-5300 specification (choose from the above).

- iMac 2008 - (20" and 24")

iMac models from the early 2008 use faster 800 Mhz memory PC2-6400 (compared to 667 Mhz modules used in 2007 iMacs). Although the above suggested 667 Mhz  modules for iMac 2007 will work in your iMac 2008 (provided both memory modules are 667Mhz) you should really look into getting the faster 800 Mhz memory - therefore the appropriate memory modules going into iMac 20" and iMac 24" aluminum 2008 models are the following (1 GB or 2 GB modules, DDR2, 800 MHz, SO-DIMM 200 pin, unbuffered):

RAM for iMac 20in, 24in 2008 models		2 GB module (800 Mhz)	4 GB kit (2x2GB) (800 Mhz)	4 GB single module (800 Mhz)
		For 6 GB upgrade use one 2GB 800 Mhz module and one 4GB 800 Mhz module.

This model as well can be upgradd to 6 GB RAM in total.

In order to max out your iMac 2008 memory to 6 GB you will need one 2GB 800Mhz unbuffered so-dimm and one 4GB 800Mhz unbuffered so-dimm memory module complying to PC2-6400 specification (choose from the above).

- iMac early 2009 - (non-wide screen models 20" and 24")

iMac models from the early 2009 use newer DDR3 memory running at 1066 Mhz memory PC3-8500. Memory modules for iMac 2009 are not compatible with iMac 2007 or iMac 2008 models. iMac early 2009 (20" and 24" inch - non-wide screens) can be maxed out to 8GB RAM memory in total.

Therefore the appropriate memory modules going into iMac 20" and iMac 24" aluminum 2009 models are the following (2 GB or 4 GB modules, DDR3, 1066 MHz, SO-DIMM 204 pin, unbuffered):

RAM for iMac 20in, 24in early 2009 models

4 GB single module (1066 Mhz)

4 GB kit (2 x 2GB) (1066 Mhz)

8 GB kit (2 x 4GB) (1066 Mhz)

iMac 2009 can be maxed out to 8 GB of RAM memory -- for which you will need two (2) 4GB memory modules 2x4GB 1066Mhz unbuffered so-dimm complying to PC3-8500 specification (choose from the above).

- iMac late 2009, 2010 and 2011 - (all wide screen models 21.5" and 27")

iMac models from the late 2009, 2010 and 2011, use even faster DDR3 memory running at 1333 Mhz memory PC3-10600. Unlike their predecessor, these iMac models have four (4) memory bays available and can be maxed out to 16GB of RAM memory.

Therefore the appropriate memory modules going into iMac 21.5" and iMac 27" wide-screen aluminum late 2009, 2010 and 2011 models are the following (2 GB or 4 GB modules, DDR3, 1333 MHz, SO-DIMM 204 pin, unbuffered):

RAM for iMac 21.5in, 27in late 2009, 2010, 2011 models		4 GB module (1333 Mhz)	8 GB kit (2x4GB) (1333 Mhz)	16 GB kit (4x4GB) (1333 Mhz)
		For 16 GB upgrade use four (4) x 4GB 1333 Mhz modules .

iMac late 2009, 2010 and 2011 can be maxed out to 16 GB of RAM memory -- for which you will need four (4) memory modules 4GB 1333Mhz unbuffered so-dimm complying to PC3-10600 specification (choose from the above).

Mixing incompatible memory modules causes system instability

iMac memory (RAM) Upgrade Guide - Simple
Step by Step Instructions with Photos

Applicable to iMac 2007, 2008 and 2009 models:

- iMac 2007 models MA876LL/A, MA877LL/A, MA878LL/A

- iMac 2008 models MB323LL/A, MB324LL/A, MB325LL/A

- iMac 2009 models MB417LL/A, MB418LL/A, MB419LL/A, MB420LL/A

Step 1 

Power down your computer.

Disconnect all cables and the power mains.

Place a soft cloth on work desk (to prevent the screen from scratching) and lay the computer face down on the cloth. 

Raise the stand upwards (in order to have access to the memory slot). 

Using the precision screwdriver take off a single screw from the memory slot plate located at the bottom of iMac bezel. If the plate won't come out easily, just use one of the smaller screwdrivers to gently pull it out. Set the plate aside.

Step 2

Untuck the tab from the memory slot(s) you need to work with.

If you need to take out some of your existing memory modules, just taken out by pulling the tab (that's what these tabs are for) applying moderate force. 

Insert (push) your new RAM module(s) into the available slot(s) until it "clicks" firmly into the place.

Tuck the tabs back above the memory slot(s). 

Step3

Install the memory plate back and don't forget that screw.

Put the computer in upright position and connect back all the cables.

Power it up. In order to verify the amount of memory installed, click on the Apple logo (in the upper left corner) and select About This Mac.  

... and you're all done! :) Good luck upgrading!

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Comments (20)

Great instructions - thank you!
written by Richard, June 12, 2008

Thank you very much for the guide, I wasn't sure which memory modules I needed for my iMac - your guide helped out!

Richard

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written by Miguel, June 12, 2008

Obrigado - thanks a lot!

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great
written by Kevin, June 12, 2008

Great work!

Thank you

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...
written by Scott, July 08, 2008

These instructions echo every other on-line instruction I have found.
I ordered from OWC, matched perfectly to the machine on bus speed and all, and when I install the 2 new 2GB modules, the machine fails to start.
If I remove 1 2GB module and replace it with the OEM 1GB module, the iMac fires up and I have 3GB or ram showing.
Is this common?
Is there a work around?

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Reply to Scott
written by Danny, July 09, 2008

Scott,

There could be several reasons for the issue you are experiencing, as follows:

1. incorrect installation of memory modules - make sure the orientation of an individual memory module is correct, also they should "click" firmly in the slot

2. incompatible modules (this is most likely the problem you're facing) - make sure you've got two modules of the same kind, please verify labels on each of the modules and make sure they are of the correct speed and also of the same CAS - CL latency (please read the article above on importance of matching the Mhz speed ans CAS - CL latency specification of both memory modules. For example - you can have two modules of the same manufacturer and of the same Mhz speed that will make your iMac act up due to different CAS - CL specification. The module compatibility issue can prove to be even more predominant if you combine two memory modules of different manufacturers.

3. faulty modules - your iMac should work only with a single memory module... insert only one of the new 2Gb modules and test out if it works... shutdown the computer, take the first module out and insert the second new 2GB module - does it work?

If one of them doesn't work that would mean its faulty and you need to return it for warranty...

However if both modules work individually in your iMac, then you are facing the memory module compatibility issue (as described above). In such case you must replace one or both of your modules to achieve module compatibility.

The best bet in upgrading iMac memory is always to purchase both modules of the same manufacturer and the same specification (you can always sell your original original memory module on eBay).

Good luck with your issue,

Danny

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dr
written by irvine eidelman, July 25, 2008

hi
i have a imac 2.4 (2007) 20 inch aluminum desktop .....came with 1g ram. On ugrading to 3G ram ie putting in a 2G plus 1G stick...all I got were beeps. Then retried...same. Then just put back old RAM same...then took to the apple shop,.....thay are still trying figure it out...any help out there?

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Reply to dr
written by Danny, July 25, 2008

You must make sure both modules are of the same speed and CAS - CL latency (please read the previous post elaborating on the module compatibility and matching) - this is most likely the issue you're facing.

Your iMac model 2007 takes only 667 Mhz modules whereas the newer iMac models 2008 take 800 Mhz modules - please read the labels of both modules and verify their speeds. In addition verify the CAS - CL latency specifications and if you have the matching modules.

You might want to try the machine with only the new 2 GB module (proving it works individually), also make sure memory modules are inserted properly into the machine (they must "click" in place).

If both modules work individually (by themselves) that would certainly mean you have the module compatibility issue and that you need to replace one or both modules in order to match the speed and CAS - CL latency specifications.

Other than that you should seek Apple service.

Danny

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You can also use 667 Mhz modules in iMac 2008
written by David, August 12, 2008

Don't be afraid to use 667mhz modules on your 800mhz enabled iMac 2008. I've tested it with complete success.

Of course you would like to use 800mhz to get all the speed from your machine, but if you have 2Gb of 667 memory on your drawer and cannot wait your new 4Gb 800mhz come from eBay, it just works.

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Problem getting the module in...
written by Eric Maginnis, October 17, 2008

I can easily follow all of the instructions, but, when I pull out the tab, it is still attached at the top of the module slot. This means that the tab is blocking the pin slot, not allowing me to put the new board in. Is it me, or does there need to be something else done with this tab to allow full access to the board slot?

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Reply to Eric
written by Danny, October 17, 2008

Eric, just pull the tab out of the way and insert the RAM.

I've found this YouTube video on iMac RAM upgrade that might be helpful to you.

Danny

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...
written by Daniel Escher, October 20, 2008

Thank you so much for this website! The instructions are super-helpful.

I want to upgrade to 4GB RAM on my iMac 2008. I am really surprised that Apple is charging $300 on their company store while Kingston charges

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written by Jim Lile, March 29, 2009

I installed two Kingston DDR2 PC2-5300 667 MHz 2GB modules in my Late 2007 Intel Core 2 Duo 24" iMac. Hoping to increase the RAM from 2GB to 4GB. When restarting, could hear the hard drive spin up, but no start-up chime and the display remained blank.
Through various trials I found that if I left the original 1Gb module in memory bay 1 (screen up, base towards me bay on the left) and put 1 of the 2Gb modules in bay 2 I could get 3GB. I thought maybe I had a bad RAM chip, but I tried both of them in bay 2 with the same results. I just can't get the 1st bay to recognize a 2GB module.
Any ideas?

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Instaling 4 GB in iMac 2007
written by Danny, April 01, 2009

Hi there Jim,

Thank you for your post! What happens if you put 2 GB memory module in bay 1 and leave bay 2 empty? Does it work? If it does, most likely you have incompatible or faulty memory modules and should seek replacement. On the other hand if a none of the new 2 GB modules works by itself in bay 1, most likely you have an issue with your iMac. However in most of the cases the problem you've described relates to incompatible pair (the modules work well individually, however when used both they're acting up), hence most likely you'll need to return your chips to the manufacturer for replacement.

Danny

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Upgrade iMac from 2 x 1Gb to 2 x 2Gb ... Machine refuses to start!!!
written by Ian, July 08, 2009

I was doing a disabled friend a favour by upgrading his ram in his 2.0 Ghz iMac from 2 x 1Gb (2Gb total) to 4Gb so he could play his movies and music easier. I purchased 2 x 2Gb sticks of 800 Mhz (was informed that this would be back compatible with 667 Mhz). When I started up (friend waiting eagerly behind me in anticipation of the great moment) the fan started but machine did not start up!!

I replaced one of the 2 Gb sticks with the original 1 Gb and machine worked.

I have placed the 2 x 2 Gb 800 Mhz sticks on eBay and have purchased 2 x 2Gb Kingston 667 Mhz sticks. Installed them both and, BAM, same thing!!! Fan starts but no boot up!!

I am now running 1 x 2Gb stick with 1 x 1 Gb stick (3 Gb in total). There seems to be no answer on web. Friend has little money to be paying for repairer to try fixing and Mac want nothing to do with us since out of warranty and Friend (Damien) did not purchase AppleCare.

Any help would be greatly appreciated.

Regards

Damien and Ian

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written by Ree, October 12, 2009

I just put in 8GB DDR2 (2x4) in my iMac 24" 2008 (8.1). Just wanted to let you know it works, even though people say it doesn't (they haven't tried, have they? ).

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8GB in iMac 24" 2008 (8.1)
written by Danny, October 12, 2009

Hi Ree,

That's great news. Other people said 8GB in their older iMacs do show up, however are unstable - that is when you fill up the RAM passed 6 GB the machine becomes unstable. You might use a memory monitor program such is iStats to see how much memory you've used - open up *lots* of programs and try to fill up the RAM pass 6 GB. At that point I wonder if you will also experience stability problems?

Thank you letting us know

Danny

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imac 07 takes 3GB but not 4GB
written by Ray, November 26, 2009

Hi Danny - have you (or has anyone) come across the problem (similar to one mentioned above) upgrading their imac 07 from 1gb OEM to 4gb (2 x 2gb) ?

If I leave the 1 GB OEM chip in and put in the 2 GB chip, it all boots up fine, and says 3GB when you look at the apple configuration. Same thing if I put the other 2 GB chip in. Both are the same Kingston chip, ordered at the same time, same model numbers (M25664G60), and assumably same CL/CAS (though I don't know how to verify this).

Why would each of them work separately with the 1 GB OEM chip, but not together?

Thanks,
Ray

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...
written by Glenn, September 12, 2010

I have an 27" iMac late 2009 I bought in Feb 2010.

Today I received in the mail 4GB of memory in 2 so-dimms. I can't get them to work. My iMac just boots and beeps every 5 seconds which means no memory. I pulled all the memory and used the 2 new 2GB memory and the iMac booots normally. I add the original 4GB and the computer won't boot and just beeps again every 5 seconds. I am thinking maybe the empty banks slots I put the new memory into are bad, but that doesn't make sense.

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Crucial Memory Advisor Tool - right memory for your system the first time
written by Crucial - The Memory Experts, December 31, 2010

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