Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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CPU Upgrade And Thermal Paste

I'm interested in upgrading the CPU in one of my iMacs (27" Late 2012) from i5-3470S to i7-3770.

I'm getting the i7-3770 secondhand for $100 and will sell the current i5-3470S for about $50, so total upgrade cost is about $50 (well, $60 if you take the screen adhesive kit into consideration).

I've opened this iMac in the past for SSD upgrade (now it has 256GB SSD and 1TB HDD (not a Fusion Drive configuration). So I won't have any difficulties opening the machine, as I've done that in the past and have the appropriate tools.

I've watched some YouTube videos and read iFixit guides, and at some point I'll need to remove the heatsink in order to install the new CPU. Upon removing the heatsink the thermal paste will break and I'll need to re-apply it.

I've noticed that Apple uses regular grey thermal paste for CPU and GPU, but uses a white-ish paste on the GPU VRAMs which can be seen in iFixit guide (step 60): iMac Intel 27" EMC 2639 CPU Replacement

Does anyone know what thermal paste I should be using on the VRAMs? I have Arctic MX-4 and Noctua NT-H1 which are considered high-end pastes. Will they work well?

I appreciate any help/input.

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For this one time application I wouldn't bother with anything else than what you'll be using for the CPU itself. The Arctic or Noctua will both out-perform whatever Apple had in there.

Otherwise my opinion is that the white past is some cheaper heat transfer compound.

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Thanks for your input. so it's fine to use the same thermal paste (MX-4/NT-H1) of the GPU/CPU on VRAMs?


Yes. I would.


Hold that thought! The white paste is a gapping paste unlike the CPU paste which is designed to be a very thin layer. Apple went to the paste instead of using pads (which I still think is better).


@danj, I'm under the impression they're using a silicone thermal compound, cheaper than the high performance thermal compound used on the GPU. And it is my opinion that doing just this one GPU replacement, he can use the Arctic compound. No need to stock on a tub of silicone.

If I am wrong, let me know why, for future reference. And I'll edit my answer too.


Yes, the compound is cheaper than the thermal paste used under the CPU & GPU, But the real reason Apple went with it was to save time and costs over using pads which are still cheaper material but takes more labor. The VRAM chips run a bit cooler as well.


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