What is the proper way to add 16GB ram to the existing 8GB in my 27" Retina iMac?

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Level 1

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What is the proper way to add 16GB ram to the existing 8GB in my 27" Retina iMac?

I've searched the web for the best answer to this question: What's the best way to add 16GB ram to the existing 8GB in my late 2014 Retina iMac (ending up with a total of 24GB ram)?

I'm seeing conflicting and ultimately confusing advice. Most people are saying to just pop in the new 16GB (2X8GB) into the 2 open slots and you're done. Others are saying no, remove the 2 4GB sticks, replace those now empty slots with the 2 new 8GB sticks, and put the 4GB sticks in the remaining 2 slots, which viewed from the bottom would be 8,4,8,4.

A third option (to make things even more confusing) seems to be keeping the 2X4GB and 2X8GB sticks together, side by side, so that viewed from the bottom you'll see 8,8,4,4 or 4,4,8,8.

I have no idea which configuration is best: They all seem to "work" according to those advocating their method. I want to know what Apple recommends, if they indeed have a preferred method.

iMac with Retina 5K display, OS X Yosemite (10.10.2), iPhone 6 Plus, MacBook Pro, iPad 3, etc.

Posted on Mar 10, 2015 5:00 PM

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Answer 1

SeaPapp

Level 7

26,486 points

Mar 10, 2015 5:06 PM in response to trex67

Don't over think it, just put the new ram into the empty slots. It doesn't make any difference.

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Answer 2

babowa

Level 9

78,103 points

Mar 10, 2015 5:54 PM in response to trex67

As mentioned, just insert the new RAM in the two empty slots which, on an iMac with vertical RAM slots, should be slots 2 + 4 (from the top) and the OEM RAM is usually in slots 1 + 3 (from the top).

You are getting the RAM from either OWC (macsales.com) or Crucial?

Here are Apple's instructions (and they assume that you are replacing all the modules - otherwise there is no mention of where to put them):

iMac: How to remove or install memory - Apple Support

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Answer 3

trex67 Author

Level 1

25 points

Mar 10, 2015 6:28 PM in response to babowa

Crucial. 16GB 2X8 204P SODIMM PC3-12800 MAC to be specific.

The OEM RAM is in slots 2 + 4 from the top, at least in mine. BANK 0/DIMM0 and BANK 1/DIMM0.

A little background: I installed new RAM in the slots last week when my new iMac arrived, in the open slots, 1 + 3 from the top. I then started up for the first time and installed my account from Time Machine. So far, so good. About 2 hours into my first day usage I started getting random crashes. By day 2 I'd had maybe 15 crashes and a dozen kernel panics. I removed the RAM and re-seated it. Same problem. I created a new user account, thinking maybe I had some corrupt data. Ran fine for a couple of hours then BOOM same problem, again. Removed the new RAM and presto, no more crashes, going on 4 days now. I returned the RAM to the vender, requesting a replacement in the hopes that I just had a bad stick (even though I ran TechTool 7 and found no problems... which struck me as weird).

So now I'm a little bit concerned about using the best, most Apple-approved method for installing the replacement RAM when it arrives. I'm not exactly a newbie. I've read things in the past about it being important to install RAM in a specific order, but it's been a while since I've had a new Mac, and things change. I want to be careful, but it sounds like it doesn't matter a whole lot. My fingers are crossed, not that I'm superstitious.

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Answer 4

babowa

Level 9

78,103 points

Mar 10, 2015 7:26 PM in response to trex67

Well, when you install it in slots 1 + 3 and 2 + 4, then your Memory info (About this Mac > Memory) will show as being matched horizontally which is how it has always been suggested. Don't ask why it is showing that way - except that Apple should have redesigned the way it is showing to account for the vertical installaation. I did a search here for Crucial RAM > iMac and couldn't find anything specific, so it might be a bad module; although one never knows with Macs being so finicky about their RAM.

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Answer 5

trex67 Author

Level 1

25 points

Mar 11, 2015 5:21 AM in response to babowa

Thank you. Your help is appreciated.

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