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Using a broken iMac's hardware as a desktop computer (kext help)

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Hi. Hopefully I posted this in the right forum :)


This is a long post, and I can't expect everyone to read through it all. So to summarize:


Got a defective 27" iMac (late 2012 with 2.9GHz i5 and GTX 660M). I want to build the hardware into a Mac Pro tower, without the original (broken) screen attached everything runs SLOW as hell. I've made some progress by deleting a few kext-files, but as I have absolutely no idea what I'm doing I hope someone here can help to improve performance even further  :)





I got a 27" (late 2012) iMac for free that a customer at our shop had dropped on the floor. The result was a broken chassis and screen, but everything else was working just fine. The customer got a new one through his insurance, so he didn't care what happened to it.


Here's a picture of it:



So after having tested that everything worked perfectly, I decided to remove the hardware from inside. Ideally I want to build this into a Mac Pro tower, and I didn't want to have a big broken screen standing around.


I was a bit concerned how the iMac would react when I removed the screen. Would I even be able to see the recovery menu on a monitor connected to the thunderbolt port? I expected that this would be a huge problem, and that the iMac would always assume the original screen was still present.

Fortunately this wasn't the case. With the screen removed the iMac just defaulted to use the one connected with Thunderbolt. This was neat, but unfortunately nowhere near perfect. Because, without the original screen in place, the iMac is missing at least one temperature sensor and it just goes ape{censored} to say the least.

This means that the fan runs at max speed all the time, easily correctable with a fan control program, but much worse, everything runs so slow that you wouldn't believe it.


I guess what happens is that the computer under-clocks itself by a large amount. And I'm not exaggerating when I say that it takes 8-9 hours to install OS X Mountain Lion from the recovery menu :o


This obviously makes the computer unusable. So I put it away in my cellar until last week where I decided to give it another go.


Reason for this, was that I was reading a bit about how to make Macbook Pros perform at full speed without an installed battery. And I thought that some of that might apply to the iMac too.


This is what it looks like on my desk atm:



So, having since then used the 1TB hard drive in my other desktop PC, I had to go through OS X install-hell once more. It took about 9 hours total, because my internet connection isn't very fast :)

I spent most of Saturday evening last weekend messing with it. It wasn't as easy as I had hoped, and when I was just about to give up, I decided to try and delete AppleIntelCPUPowerManagement.kext and AppleIntelCPUPowerManagementClient.kext. Why? Because I seemed to remember these two files being mentioned in the Macbook Pros case.

I restarted and to my big surprise this actually improved the speed of the computer by a lot! It still isn't perfect, but at least it's somewhat usable.

Intel Power Gadget says that my CPU is now running at 1.6GHz, it should be 2.9. 


I tried running GFXbenchGL from the App store. I had tried this when the original screen was connected, so I know that it should be able to run the T-rex scene at about 60fps.


It ran it at about 9-10fps :/


Then I found the file called AppleGraphicsPowerManagement.kext. I didn't give it too much thought, the computer was still not working as desired, so I deleted it and rebooted.


Now the T-rex scene runs at about 30fps!


Still that's not really good enough :/


I found this site: osx86.tistory.com/243 which has a description of a lot of the kext files. 


And I've tried deleting several of those with not so great results :P This resulted in many cases where I had to wait another 8-9 hours for OS X to reinstall, all while the fan is going crazy  :D Now I've finally gotten tired of that, so I have several back-up images, at various stages, on an external hard drive, so I can quickly get it back up and running.


I hope someone here will be able to help me get this thing up and running perfectly :) The chassis and broken screen was thrown away months ago. This is a list of the components I still have:



Power supply


Ram (not the original, gave those away) 3x 2GB 1333MHz DDR3.


Webcam and cable

Monitor cable that was used to attach the 27" display to the motherboard.


Here's what I don't have anymore:




Microphone (unless it's attached to the motherboard or webcam?)

Headphone socked (actually a damn shame, because Apples headphone amplifiers are very nice, and now I'll have to find a cheap USB DAC instead. Unless someone happens to know the pinout of the connector on the motherboard? :) )


So yeah that about sums it up. It's still a pretty decent computer by todays standards, so I would hate to throw it away. I assume that the answer lies with the kext files somehow, and I hope someone here has enough knowledge about this, and can guide me to get 100% performance out of my system, because I sure as hell don't know what I'm doing :)


I don't suppose anything can be done about the extremely slow Recovery menu and OS X installation. Upgrading from Mountain Lion to Yosemite is another 7 hours btw. But I can live with that since it's only needed a few times a year :)


Thank you for your time.

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Sounds like an interesting project. Not too sure how the iMac motherboard was mounted, but I am sure you can fit it into a PC chassis/(If that is your intent)

I suspect that you don't have any PCI slots on that motherboard or do you?


Since it IS Apple hardware, you don't need to worry about kexts as you should be able to install MacOS X just like was an iMac. This is not a hackintosh.


If you can get the parts mounted and connected as they were inside the iMac, you can replace the video cable so that it will reach an external monitor. One thing to consider though is how to start up the computer. You need a power button.


I just recently built a hack inside an oider Apple G5 case (2005) and everybody I show it to, loves the concept.

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Since it IS Apple hardware, you don't need to worry about kexts as you should be able to install MacOS X just like was an iMac. This is not a hackintosh.

As I said, I already got it up and running, and there are noticeable problems. Removing the screen makes this not so plug and play anymore, so some fiddling with kexts appear to be absolutely necessary (as described in detail above).


I do have a power button soldered to the power supply as you can see here (left of the harddrive):



Should get a Mac Pro tower next week :)

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I found this:



Maybe it will work, even though the iMac already has a 64bit bootloader?


As long as it ends up working perfectly, all hardware works as intended, and I can install every update with little hassle I don't really mind how it's achieved :)

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Yes I have. Thanks for the suggestion though :)


I tried following the guide I posted above to create a bootable Yosemite USB drive that should work for old Mac Pros, but that didn't work for me.


I managed to install Clover on an EFI partition, and I've managed to trick the iMac into thinking it's a Mac Pro 3.1 :)


For this to even boot I had to disable all ACPI options, so not sure if it's gonna help anything. I still don't have any improvements in performance, but again, I'm not really sure what I'm supposed to enable here :)


Perhaps I should try to extract a DSDT file from my Mac if possible? Wouldn't that make it a whole lot easier? But as I understand I can't do this on Yosemite:


So for this I would have to reinstall my Mountain Lion image as far as I understand.

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Hmm I'm stuck. I really have no idea what I'm supposed to configure in clover :/
I got clover installed to an EFI partition and I can boot from that (after disabling all ACPI options). I got Clover Configurator installed, and I got the DSDT.aml file extracted, and put it in EFI/CLOVER/ACPI/patched/ (attached to this post).


I've tried various CPU and GPU settings but they haven't helped. After booting with Clover the CPU frequency changed from 2.9GHz to 2.89 so I tried changing that. Not really sure what "Bus Speed kHZ" means, and reading about in the clover wiki didn't make it any clearer for me. So I chose not to touch that setting.


Again, any help will be greatly appreciated. I feel like I've yet again moved a step in the right direction :) I assume Clover works, since the iMac is now identified as a Mac Pro :)


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it's always stupid when a senor is defective or lost, but here is a solution to your problem: install "SSD Fan Control", then start the app and activate "Manual" then you will notice the difference, the tool provides very good job.


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There's nothing inside the cable unfortunately. And of course I have thrown away the LCD logic board long ago, so I can't check :D


I guess the easiest solution would be to get a logic board from a broken 21.5" screen and just install that inside the case :D That would of course mean that it would render 3 displays at once (I have two hooked up to it). I don't remember if you can disable the built in iMac screen altogether, but either way it should still be a noticeable performance increase compared to what I have now :)


Haven't had time to check why Clovers auto config failed. I haven't forgotten though :)


And thanks everyone who posted in this thread so far! I didn't expect so much help :)

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Hi, haven't had much time to play around with this for a little while.


I haven't really made any new progress, but I managed to clarify a few things.


Last week I bought a new Macbook Pro 15", the one with dedicated ATI GPU and 2.5GHz i7. Its quite nice and I like it a lot.

I tried running the CompuBenchCL test on it, and realized that it was stuttering pretty bad on it too, although not as bad as it's clearly more powerful. This is apparently normal behavior for this test, because the Macbook Pro runs everything else with ease :)


This led me to believe that maybe the processor in my iMac wasn't running at a lower clock speed after all. The program Intel Power Gadget gave me that idea because it said 1.6GHz. I have now tried macCPUID (which is also Intel) and HardwareMonitor, both says that the CPU runs at 2.9GHz :)


I also tried the Intel Power Gadget on my new Macbook, and while it did display the correct clock speed, the program was doing all kinds of messed up things, so I think its safe to assume that the program is buggy and that's what lead me to believe the CPU was running at approximately half speed. Makes sense as I couldn't feel any problems while using it for web browsing.


So is the GPU running too slow? Well, it's hard to say. It ran the T-rex scene perfectly back when I tested it with the original screen attached, but that could have been a much older (less demanding version of the benchmark program), and it could also possibly still be the smaller amount and slower RAM. Don't know, will have to do more testing :)

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You are going through a lot of headaches. Here is my take for what its worth. Since you got this iMac for nothing you can get a screen from the above link or maybe cheaper on eBay; I would look at OWC for upgrading if it has a fusion drive and also the SSD card that on the other side (full disassembly) to get at it. 

Yes the camera may well be built in since the glass is "welded" to the display. I have taken earlier iMacs 20 & 24 inch screens for hard drive upgrades. There may be something of a sensor causing the slowdown. You could put a display in front of the cracked screen. Just my 2¢ worth.


I have made "Hackintoshes" with either Tony Mac or Kakewalk and they served me well. I have used a hacked boot EFI to keep a 2006/2007 32bit EFI MacPro Tower running.  I am slowly approaching my 7th decade and that Mac Pro was killing me( I used it to teach Photoshop, MacOS X and even Windows in Parallels) so I waited for the new Mac mini but was disappointed that Apple made another road apple (soldered RAM) so I opted for a 2012 i5 MacPro 13" laptop and immediately removed the CD/DVD writer moved the mechanical drive in its place and installed a Samsung EVO 500GB drive only to see no TRIM support until El Capitan (15A282a) that I am running. I had to use Cindori Trim and later Disk Sensei.

Soon as Apple Care expires on my 2012 refurb 27"iMac and those SSD drives increases sizes I may be taking the guitar picks and removing the screen but thats later. Good luck.

--lou cioccio

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Hi, thank you very much for the suggestion. Unfortunately I don't have the frame from the computer anymore. It was completely bend and busted from hitting the floor :( Had that not been the case, then I would probably go for a replacement screen, since they are pretty good screens as well :)


I have ordered 2x 8GB RAM today, and as I mentioned earlier a friend of mine has acquired a Mac Pro tower that I can build it into. So I'll proceed with that. As far as I can tell it's running the desktop perfectly fine, I'm just not too sure about the applications that relies heavily on the GPU. But that's not really a huge problem for me.


I would also like to thank spakk for mentioning and getting me to try SSD Fan control again. While I don't like the configuration interface at all, this program start up before logging in to the computer. This means that the fan will never reach max speed, even if I leave it at the login screen. This solves an otherwise annoying noise problem :)

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Is it possible to upgrade the CPU in an iMac? I mean since it's socketed, it's doable, but I'm unsure if there's anything in the software that prevents one from doing it.


Would be nice to install a 3.4GHz i7 at a later point :)


I should get all the parts tomorrow, including the Mac Pro tower. So I can finally start putting this together :)

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  • 1 month later...

Why install clover or even choose diff smbios, totally confused.

smbios is important for power management, and your not changing cpu etc.

Modern o.s dont care if a screen or other hardware comes and goes, this is normal.

If it takes forever to do things, consider it has some other damage from the fall. 

An operating system is not aware if it is in its original chassis or in a cardboard box.   :blink:

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  • 3 weeks later...
  • 3 weeks later...

I only installed Clover based on suggestions in this thread. I have removed it since.


I don't have that wire can't remember if that was present on mine. Fairly sure it only slowed down when the screen was removed, and that there was a thermal sensor on the LCD driver board.


Is that picture from a 2012 iMac?

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Unfortunately I don't have the LCD driver board anymore :/


I guess I should start looking for a defective 2012 27" iMac.


I have the system up and running. It's working somewhat fine if I delete the kexts, but it only runs at 1.6GHz :/


For normal everyday use it's alright, but running demanding stuff just isn't possible.

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