daikambu65
Level 1 (10 points)

Q: Must RAM chips be symmetrical - user installed

Late 2013 iMac 27" with trap door on the rear for RAM.  Running Mavericks.

 

I currently have 2x4Gb chips. I am finding that the machine struggles when running a certain applications. I want to incrementally add
RAM until I learn how much is needed. I can't afford to just throw in 32Gb as many folks advice. So I would like the first step to be an 8Gb chip. If more is needed, I would then like to add another 4 or possibly an 8.

 

Will this present a problem? Having 2x4 + 1x8?

Aperture 3, OS X Mavericks (10.9.1), running an iMac

Posted on May 13, 2014 10:55 AM

by baltwo,Solvedanswer
baltwo baltwo
Level 9 (62,256 points)
A:

Ah! Apple cheapskates no longer providing users with useful info. Based on what I found in http://support.apple.com/kb/HT1423 and http://support.apple.com/kb/ht3011, what the so-called geniuses told you doesn't match this statement:

 

The iMac (27-inch, Late 2012) and iMac (27-inch, Late 2013) have four SDRAM slots, each of which can accept a 4 GB, or 8 GB SO-DIMM.

 

That means you put any combination of 4 and 8 GB modules in those four slots.

Posted on May 13, 2014 12:57 PM

Close
daikambu65

Q: Must RAM chips be symmetrical - user installed

  • All replies
  • Helpful answers

  • by baltwo,Helpful

    baltwo baltwo May 13, 2014 11:53 AM in response to daikambu65
    Level 9 (62,256 points)
    May 13, 2014 11:53 AM in response to daikambu65

    Information is in the About this Mac booklet that shipped with the machine. Alternatively, DL the appropriate one from http://support.apple.com/manuals/

  • by daikambu65,

    daikambu65 daikambu65 May 13, 2014 12:33 PM in response to baltwo
    Level 1 (10 points)
    May 13, 2014 12:33 PM in response to baltwo

    Actually, Apple only supplies a Quick Start Manual. With very little information. The "27 inch model with the trap door isn't real common. Thus user-installed memory is rarely talked about.

     

    I have AppleCare and just got off the phone with them. Here's the definitive answer:

     

    The machine can have 2 RAM chips installed. Or it can have 4  chips. And they must all be the same. So, Symmetry is a required specification.

     

    I have to jump to 16 Gb if I want to play it safe. By adding 2x4. If that isn't enough, I have to jump to 32 (4X8). Unless someone out there sells 6Gb RAM chips.

     

    But while talking, I realized I can sell my used RAM on eBay to recoup some of the cost.

     

    Thanks for pitching in.

  • by baltwo,Solvedanswer

    baltwo baltwo May 13, 2014 12:57 PM in response to daikambu65
    Level 9 (62,256 points)
    May 13, 2014 12:57 PM in response to daikambu65

    Ah! Apple cheapskates no longer providing users with useful info. Based on what I found in http://support.apple.com/kb/HT1423 and http://support.apple.com/kb/ht3011, what the so-called geniuses told you doesn't match this statement:

     

    The iMac (27-inch, Late 2012) and iMac (27-inch, Late 2013) have four SDRAM slots, each of which can accept a 4 GB, or 8 GB SO-DIMM.

     

    That means you put any combination of 4 and 8 GB modules in those four slots.

  • by daikambu65,

    daikambu65 daikambu65 May 13, 2014 1:13 PM in response to baltwo
    Level 1 (10 points)
    May 13, 2014 1:13 PM in response to baltwo

    These links skirt the question of symmetry. They also aren't clear on how many chips are required. Is 1 OK? 2? 3?

    Of course the machine comes with 2. And they mention having 4. But what about 3?

     

    And nothing at all about them all being the same size.

     

    Meanwhile, it was a bit of a revelation to read what the Technical Info at the Apple Support center says about memory management in OS Mavericks. I was taking a static view of memory. Apparently, Mavericks juggles RAM according to use, and switches off memory temporarily as the tasks change. And I guess pieces are held in a sort of Cache. In the end, it squeezes every last drop out of a scarce resource.It is dynamic, so the static specifications aren't a hard and fast limitation.

     

    Hey, these folks must have seen my juggling bills and my meager checkbook. I want credit!!!!

  • by baltwo,

    baltwo baltwo May 13, 2014 1:17 PM in response to daikambu65
    Level 9 (62,256 points)
    May 13, 2014 1:17 PM in response to daikambu65

    Since the documents don't explain that, you'll have to discuss the symmetry issues with AppleCare. I have an iMac w/2 x 2 GB and 2 x 4 GB modules. I've not tried a 3 x 2 GB and one 4 GB combo.

  • by daikambu65,

    daikambu65 daikambu65 May 13, 2014 2:07 PM in response to baltwo
    Level 1 (10 points)
    May 13, 2014 2:07 PM in response to baltwo

    You have a different year iMac. It seems from the list of models at Apple Support, each model has different specs for the DRAM and different install configurations. And OWC offers yet other advice.

     

    They say you can (on my  late 2013 at least) pair up 2x4Gb chips with 2x8Gb chips. If I am reading them correctly.

     

    Thanks for your input.

  • by baltwo,

    baltwo baltwo May 13, 2014 2:16 PM in response to daikambu65
    Level 9 (62,256 points)
    May 13, 2014 2:16 PM in response to daikambu65

    OWC and the Apple doc say the same thing. That's why I suggested another call to AppleCare.

  • by daikambu65,

    daikambu65 daikambu65 May 13, 2014 3:12 PM in response to baltwo
    Level 1 (10 points)
    May 13, 2014 3:12 PM in response to baltwo

    On my 2nd call to AppleCare I was connected to a technician who owns the same computer. A 27" Late 2013 iMac.

     

    He said I can mix and match whatever I want. 2x4Gb + 2x8Gb. Three chips, two or 4. It makes no difference. He has 32Gb in his own machine. And he suggested that for my purposes, 16Gb would do a great job.

     

    Keep in mind that this advice only applies to a Late 2013 iMac 27".

  • by baltwo,

    baltwo baltwo May 13, 2014 3:51 PM in response to daikambu65
    Level 9 (62,256 points)
    May 13, 2014 3:51 PM in response to daikambu65

    thumbsup.gifThere you go. As I noted earlier, according to the linked doc, I suspect it also applies to the iMac (27-inch, Late 2012).