I noticed my iMac being slow. I thought it was just me? You know, after a few iterations of upgrading operating systems etc. Things slow down. That's just what happens. So I put clean-installed SSD in it. I done that previously for my aging MacBook Pro with fantastic results. To my dismay my iMac still felt slow. So I looked around for a benchmarking utility to quantify this feeling I had. I found geekbench 3. That software confirmed that my iMac was running way slower than it should - less than half the speed you'd expect.

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    • I used DropSync 3 from the Appstore.

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  2. Geekbench 3 32-bit test. Geekbench 3 allows you to browse results from others with similar computers, so it was easy to see that something was wrong with my mine.
    • Geekbench 3 32-bit test. Geekbench 3 allows you to browse results from others with similar computers, so it was easy to see that something was wrong with my mine.

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    • Naturally I asked on the iFixit forums and elsewhere about what might be wrong. Though helpful, the forums spun off in irrelevant directions, mostly talking about hard drive install issues. Geekbench 3 dosen't benchmark hard drives so...

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    • There's loads of videos and iFixit repair guides to show you how to get in to your iMac so I'm not going to go over that ground.

    • Be super careful with that ridiculously flimsy ribbon cable on the top left

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    • To remove the mother board undo the Torx T10 screws shown in the yellow circles. (There's one behind a cable bottom right)

    • Hopefully I've circled them all. (undo any screw on the mother board that has a white circle printed on the board.)

    • Oh, you'll also have to yank out the infra-red sensor behind the Apple logo. Just pull up. It's spring loaded in there...

    There should be a total of 8 that have to be removed the 8th one has a small triangle pointed at it on the right side of the left radiator frame

    Fetlifer - Reply

    • Label all the cables as you remove them. Work logically. I started top right and went anti clockwise. (this helps to know you haven't missed any when you reassemble.)

    • Theres 2 that have the gold contacts in the clip facing the motherboard... I noted that too. Probably important not to turn them around?

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    • There's three more behind the motherboard too.

    • (hard to photograph)

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    • Once you have the motherboard out you should have something that looks a bit like this.

    • The CPU is the one that's mounted at the funky 45° angle. Bottom left on the overall photo.

    • On the side of the motherboard that normally faces the back case there's huge Phillips head Spring loaded screws holding the heatsink on, but on the other side the usual torx T10 back to back with the Phillips head things. Four to undo.

    • When you have that heatsink off you need to clean the heatsink side with some thermal cleaner. Fixit sell it.

    • The i7 processor is socketed and easy to unclip. There's a spring loaded handle top right orientation in the overall photo although you can't see it because of the heat sink. In the 4th image it's visible to the left of the socket.

    • The old processor lifts out and the new processor drops in be careful to align the processors identically. One corner has an arrow on it.

    • Use new thermal paste between the processor and the heatsink. IFixit sell it.

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    • After reassembly redo benchmark

    • Much better!

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To reassemble your device, follow these instructions in reverse order.

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Member since: 11/04/2014

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Tried it out. Unfortunately my iMac Intel 27". EMC 2309 (Late 2009, Core 2 Duo 3.06 GHZ) Had an older Socket (775).

Walter Siegenthaler - Reply

Bad luck. I did read on blogs some conjecture about weather the processor was socketed or not. It turned out it was socketed, which made it very easy to replace. All I was doing was replacing like-for-like processor. I wasn't trying to upgrade or anything. As you can see from the benchmarks even replacing like-for-like can be advantageous. (also inexpensive because these are not new processors now!)

Perhaps replacing your old processor with a fresh one of the same sort will improve things? It's worth a try if you got this far? It certainly worked for me. It's not fast by modern standards, but totally useable for a 7 year old machine is pretty good I think... Certainly never happened when I had windows machines!

mark -


how did you find out that you had “iMac Intel 27". EMC 2309 (Late 2009, Core 2 Duo 3.06 GHZ) Had an older Socket (775).”?

I have the same computer with Core 2 Duo 3,06 ghz and I’m considering CPU upgrade to Intel i7 processor.

Ludvig Petersen -

i just tried a intelcore 2 quad 2.83ghz(q9550s) socket 775...imac wont boot starts,but only got 2leds doesnt go to 3 and nr 4 leds... :(

bleach24 - Reply

I was wondering if a replacement could bring VT-X EPT capabilities, or that is not possible because of the lack of firmware support. My replacement i7 does support EPT, and still I cannot use it with let's say Dockler for Mac. Any ideas how to fix that?

Zsolt Kovacs - Reply

Unless you are really adventurous, you should only swap out the processor in a Mac with one that was originally offered for that Mac model. So for your Core 2 Duo late 2009 iMac, I would only try one of these (preferably the faster one if you can find it of course):

3.06 GHz Core 2 Duo (E7600)

3.33 GHz Core 2 Duo (E8600)

Matt G - Reply

Did you actually replace the CPU with an identical CPU? Your Geekbench screen shots both show i7-860 2.8Ghz processors. If so how does installing an identical processor improve the benchmarks?

jliddard - Reply

Not sure. I guess I must have cooked the old processor somehow? The old processor still worked but was SSSLLLLOOOOWWWW! I don't pretend to know how it all works in there, but I guess there must be some kind of error correction loop within the processor?

What I do know is that I did what you see in the guide, replacing the processor with a new identical one, and the computer is still working at the increased speed now almost 2 years later. it's a little steam-driven by modern standards, but still useful. $50 well spent!

mark -


this post is very interesting, I have an iMac (27” late 2009) with an Inter Core 2 Duo, would it be possible to swap it for a newer CPU? like an i5, I don’t want to get read of my iMac it was a birthday gift from my grandparents and sincerely it still has a lott to offer. I was planning on upgrading the main HDD for an SSD and taking the RAM from 8GB to 16GB. the las thing it would need is to upgrade the CPU, would it be possible to do so?

Riccardo Finotti - Reply

You can’t do that Robert.

applerepairshop -

Is there software that will tell you the kind of socket that your computer has? Or do you have to go chip diving?

lawlessmark - Reply


Look on the bottom of your iMac stand.

if yours says EMC 2374, it supports i5 & i7.

if yours says EMC 2309, it supports C2D.


Just go to the “About This Mac” and see if it says CD2 under CPU

applerepairshop -

I found this guide looking for any tips how to solve problems with my iMac which suddenly became very slow. As author I have late 2009 model with i7 2.8Ghz processor.

My current Geekbench results are: about 880 in single core and about 3160 point in multi core test. Thanks to author now I know that problem lie in processor which (I think) has been cooked (my iMac for years has problems with temperature sensors). I will replace it by new one and will see…

Tomasz Wojtkowiak - Reply

I currently have a C2D version of this iMac. I know I can’t change the CPU to an i5/i7 on the current motherboard. My question is could I swap the whole logic board essentially upgrading from an EMC 2309 to EMC 2374. Would everything fit/work?

Jose Jacob - Reply


I used mark’s guide for iMac’s intel processor replacement. The case where the benchmarks are about half of the expected ones, are because the iMacs’ i5 or i7 enters an “safe mode”, all cores working but lower frequency. When I tried yesterday to upgrade my late 2009 iMac’s cpu from i5 760 to i7 860, I had the same terrible Geekbench results as mark. But… It was the skin temperature sensor (*TS2p) whose pin had been bent by me during the assembling. I fixed it with a little bit of soldering and I now have excellent results!

supersof - Reply

Wow! respect for the soldering, and the upgrade! Thought that was a step too far by many accounts I read. Glad it worked for you. Good also to have the first rational explanation for the slow speed, but working mode it was in. Don’t think it can have been bent pins or whatever in my case… The limp-home mode seems totally plausible I think.

mark -

Great thread. Just replaced my HDD with an SSD and fresh OS install on my late 2009 27 inch iMac. Performance improved greatly. Next I’m going to swap my core 2 duo 3.06 for a 3.33. Dunno if it will too much of a difference but every little bit helps. I’ll update my results! Thanks for all the posts! Robert

Robert Fulton - Reply

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