CPU upgrade 2.0GHz to 2.8Ghz ( C2D Extreme X7900 )

"Yes! I was able to swap out the processor on my T7300 20"" mid 2007 imac to an X7900 by following the instructions for replacing the heatsink here:

iMac Intel 20"" EMC 2133 and 2210 Heat Sink Replacement

When the heatsink is removed, the CPU is exposed. Turn the slotted screw on the socket 180 degrees to release the CPU and install the X7900.

I do have a caveat: The connectors on the wifi and bluetooth antennas are extremely delicate and hard to get off/on. I just unscrewed the daughter boards, there is enough slack to leave them attached to the antennas.

After the install and reassembly, the computer booted up fine, there were no settings to make, firmware flashes or any other special procedures, just turn it on and bask in the glory that is the Core 2 Duo extreme.

Update

Yeah, it runs just great. No heat issues or any glitches. The 64-bit geekbench score when from 2749 to 4239, an improvement of 54%. I also put a 4GB in one slot and a 2GB in the other for 6GB total RAM."

"Well its done! The T9300 is in and macOS Sierra is running smoothly on my 2007 iMac. It does benchmark a little less than the X7900 but the T9300 runs much cooler. I will like to give it more time before I say for sure but I am thinking that it runs macOS better than the X7900.

Im not experiencing beachballs or lags like I was on El Capitan.

If anyone wants any more info just let me know. Im gonna work on it a few days and see how the experience is all around. And then do a final impressions in about a month"

"I know this is an old guide, but just wanted to post that I just upgraded my old 20"" iMac EMC 2133 from a 2.0 GHz T7300 to a 2.6 GHz T7800 and it works great. The T7800 was never officially offered in the iMac, but it was offered in the MacBook Pro of the same era, so the OS and firmware seem to know about it. Right now a used T7800 goes for about $21 while the X7900 still sells for $70, so it seemed like a good deal coming from 2.0 GHz.

At the same time, I upgraded the original (probably failing) hard disk to a 480 GB SSD. Running 10.10 the machine has gone from unbearable to actually useful for daily work. Pretty awesome for a 9 year old computer and bought me time to save up a little extra to upgrade to a Retina iMac instead of the standard res I would have bought today if the upgrade didn't work.

Edit - as requested, here is what my system profiler shows post-upgrade:

And here is an image of the iMac all torn apart. This isn't an upgrade for beginners, but it's not really any harder than doing a logic board swap in most laptops - you just need the Torx drivers while most PC laptops stick with Phillips.

Finally, here is the new CPU in its socket before thermal paste."

"Just to update, its almost 4 years later that I posted here and the x7900 is working great for El Capitan. But I am moving on. I just ordered an E8135 cpu and am going to be installing it soon so I will then be able to install macOS Sierra on my 20"" 2007 iMac. I am also going to be doing a wifi/bluetooth upgrade with a combo card out of a 2013 MacBook Pro.

**********UPDATE**************

The E8135 does not work. I think its because the FSB on the E8135 is 1066 and our 7,1 iMac FSB is only 800. I tried a few things but never got it to boot up completely, I am waiting on a T9300 now. which has the same FSB and supports sse4.1 for macOS Sierra. I will keep this thread updated when the parts come in on the 17th. Im also upgrading the wifi/bluetooth to a combo card from a 2013 MacBook Pro. So it should support handoff and continuity."