iMac Processor Upgrade Details

I am planning on doing a processor swap in a 2006 Core Duo imac. I've found several links that discuss successfully upgrading the processor to a Core 2 Duo processor and being able to run an install in Firewire Mode to OS 10.7 Lion. I'm hoping for some help on what processors will run in this machine. Their are a lot of Core 2 Duo processors around that are pulls from PC's, and these are much cheaper than pulls from Mac's. Below are several questions I need help with:

Can i install a Core 2 Duo processor with the same ZIF socket from machines that are non-Mac?

Does anyone know where i can find information on what ZIF Socket pattern my iMac uses?

My iMac uses a 667MHz system bus, does the processor i install have to have that same rating, or will 800MHz processor run?

My Machine: iMac 20' 2.0 Core Duo (Early 2006 MA200LL, Processor T2500)

Thanks for any help you can provide.

I'd be interested in seeing what can be done myself as I have the same machine. I just put an SSD into it to replace the original 250gb HD. It really makes a difference as disk access is a bigger bottleneck than the processor.

Is Lion restricted to a Core 2 Duo and up, or is it the architecture that is built into the later machines that it needs as well, such as bit width?

Do you know for a fact that your iMac Core Duo uses a ZIF socket to mount the CPU? Did you check the logic board layout at iFixit: The free repair manual?

Also: Even if you are somehow able to install a Core 2 Duo CPU in your iMac, the firmware will continue to identify it as a Core Duo and Lion will still refuse to install.

Re:

Yes i know for a fact that it does have a ZIF mounted CPU, many iMac's have a removable CPU. See link here to specs: iMac "Core Duo" 2.0 20-Inch Specs (Early 2006, MA200LL, iMac4,1, A1174, 2105) @ EveryMac.com

Also, you are correct about the Lion installer still recognizing the machine as having a 32-bit logic board. However, Lion does not need a full 64-bit machine to run, just a 64-bit CPU. Several people have had good look by installing a 64-bit CPU and using the FW target mode from another disk to fool the Lion installer. I don't see why this wouldn't work. See link for discussion: https://discussions.apple.com/thread/3188682?start=0&tstart=0

Exact same setup. Attempting upgrade next week.

I'll be able to answer your 800mhz fsb question by the end of this week. The processor that comes with this particular imac that you mentioned is the Core Duo (T2500). Here's an entire spec sheet on this exact model: iMac "Core Duo" 2.0 20-Inch Specs (Early 2006, MA200LL, iMac4,1, A1174, 2105) @ EveryMac.com

The socket is a removable (read: zif) socket. The chip I'm replacing it with is this one:

Intel® Core™2 Duo Processor T8100
(3M Cache, 2.10 GHz, 800 MHz FSB)

The T8100 wasn't ever introduced into the imac line, but is about as high as you can go, and still have it be Socket P, like the T2500.

Package type 478-pin micro-FCPGA (aka: socket P)
Socket type Socket P

It will fit. Everything is hunkered down on whether or not the imac will be angry about having 800mhz fsb.

Wikipedia states this on the list of Intel core 2 duo processors:
"Penryn" (Apple iMac specific, 45 nm)
Die size: 107 mm2
The 2008 20" iMac used the E8135 and E8335 CPUs at a lower than specified clock frequency, explaining why the same model is used at different frequencies. This list shows the frequencies used by Apple.

The clock frequency, however, is shown to be 1066 on that "imac specific" version. Note the year however: 2008. Not early 2006.

So, quite honestly, it's a shot in the wind. ;P But I'll be sure to report back with results by the end of the week or so!

Nope.

Alright, I'm back.

It's absolutely CRUCIAL that the FSB be the exact same. It will not compensate by downclocking the processor. It will just flash once, and fail to boot.

Again, 800FSB will not work. The processor MUST be the ~667 version, like the T5850 (or whatever it's called).

Now the real question is... after the upgrade, what further steps must be taken in order to get LION running perfectly? The motherboard will still be classified as incompatible, regardless of the processor we drop into it. That's solvable at the moment by ridding ourselves of the .plist file that looks for compatibility... my question is... will the OS recognize a 64-bit processor?

No, it's in the firmware and will show it's a Core Duo Mac. My Mini was the same way.

I will have to find the URL but you just make a Lion Flash Drive and delete one file and it will boot. Will see if I can find it and post back. I did my mini the hard way and put the drive into an external case and on my iMac and installed Lion. But later I still had to delete one file to get the mini to boot from Lion.

dtravis7 said:

No, it's in the firmware and will show it's a Core Duo Mac. My Mini was the same way.

I will have to find the URL but you just make a Lion Flash Drive and delete one file and it will boot. Will see if I can find it and post back. I did my mini the hard way and put the drive into an external case and on my iMac and installed Lion. But later I still had to delete one file to get the mini to boot from Lion.

Click to expand...

Oh yes please! Post back when you find that. It would make it much, much simpler.

Apologies for resurrection, but any updates on this? I'm interested in upgrading my Core Duo 2.0 20" for Lion. Probably looking at the T5850 ($15 on ebay, nice).

Also... I feel like something even simpler (at least for me) than using a flash drive or removing the HDD is using the godsend miracle known as Target Disk Mode, if you've got another Mac somewhere nearby. I firewire'd it up with my C2D 2.4 MacBook and simply chose my iMac's drive as the install target, and it went without complaint.

As a side note: will upgrading the CPU allow me to throw 4GB RAM into this bad boy, or is that a limitation of the mobo itself? I've already got the 2GB chips, it's all I can do to keep them from jumping into the bay themselves.

P.S. the file to delete would be /System/Library/CoreServices/PlatformSupport.plist. Optionally you might mess with InstallableMachine.plist as well.