I just finished upgrading the Intel processor in my iMac from a 2.7 GHz i5 to a 3.4 GHz i7. There are a few guides on how to tear down your iMac on the web, one of the best courtesy of the folks at iFixit. Enough has been written about the process that I’m not going to try and write it down here. However, I will share some lessons learned while doing the upgrade.
- You can’t differentiate between the left and right speaker connections. Make sure you label at least one of the channels to avoid having to guess.
- Check all the motherboard connections. After you have reinstalled the display panel (a 15 minute job) is not a good time to realize you didn’t connect a heat sensor or fan.
- Remove and reseat your memory. It is very tricky to reinstall the motherboard, as the bottom edge needs to fit into four slots. You will most likely knock your DIMMs around trying to fit the motherboard in.
- Make sure your memory matches, and don’t use cheap bargain memory. I installed Corsair memory in addition to the stock Apple memory, and had apps crashing continually. Remove the Apple memory and all is good.
- If you can, wear rubber or surgical gloves when handling the display, otherwise you will have fingerprints behind the glass.
Going from the i5 to the i7 gives a nice boost. The i5 has a 6 MB cache, while the i7 has 8 MB. A larger cache does help with the speed, but not as much as multithreading. The i5 has four cores, each with one thread; the i7 also has four cores, but it has two threads per processor and supports hyper-threading.
I didn’t think that there would be a massive boost, but the multithreading does a great job. You can see for yourself by viewing these Geekbench benchmarking results:
Well, that’s all for now… I need to go and open my iMac up again. My optical drive fan is going full speed because I forgot to connect the heat sensor.
Maybe I should follow my own advice!


