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Old Nov 30, 2012, 01:42 AM   #1
rick.m650
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27" RAM Upgrade - why not 24GB?

I don't see why no one in this forum intends to add 2 x 8GB chips and keep using the 2 x 4GB chips that come with the iMac. Waste not want not... is there a problem with running 24 GB?
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Old Nov 30, 2012, 01:50 AM   #2
SR20DETDOG
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is there a problem with running 24 GB?
Nope, I'd be very surprised if the new iMacs couldn't run different pairs of sticks like that. Many people have upgraded their 2010/11 iMacs to 20GB (2x2GB & 2x8GB) and I intend to do the same.

As for why people aren't going for 24GB,I have no idea, but then I haven't really been following the 2012 iMac news.
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Old Nov 30, 2012, 02:27 AM   #3
Roller
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I don't know if there's any performance penalty running two pairs of memory sticks of different sizes. If not, I'm going to add two 8GB sticks for a total of 24GB. I usually order from OWC, but they're not listing the 1600MHz memory that the 2012 iMac uses yet, but I'm hoping that it's not much more expensive than the 1333MHz memory.
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Old Nov 30, 2012, 11:13 AM   #4
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I intend to do the same.
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Old Nov 30, 2012, 11:55 AM   #5
medi.freak
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That's what I will do...

You get 24GB for just 68,99 (amazon.de)


not really worth spending 140 tog et 32GB and ditch the 8GB it came with IMO
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Old Nov 30, 2012, 12:06 PM   #6
Galatian
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Ever heard about dual channel?
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Old Nov 30, 2012, 12:09 PM   #7
jedolley
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Since I got two kits of 2x8GB for $89, I'm going to run 32GB. Had I gotten the RAM at regular price, then I may have considered just 1 kit.
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Old Nov 30, 2012, 12:13 PM   #8
lixuelai
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There is no performance hit for running 24GB of RAM if the RAM is installed properly. Ivy Bridge is dual channel so make sure you have 12GB installed on each channel.
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Old Nov 30, 2012, 12:23 PM   #9
Galatian
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There is no performance hit for running 24GB of RAM if the RAM is installed properly. Ivy Bridge is dual channel so make sure you have 12GB installed on each channel.
That's because memory sticks come in 12GB size?!? They usually only come in 2, 4, 8, 16 GB sizes at the moment. Tell me how you can get a 12 GB module? :-D

Just make sure that both the sticks that form a dual pair are the same size and preferably from the same manufacturer and you'll be fine
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Old Nov 30, 2012, 12:24 PM   #10
lixuelai
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That's because memory sticks come in 12GB size?!? They usually only come in 2, 4, 8, 16 GB sizes at the moment. Tell me how you can get a 12 GB module? :-D

Just make sure that both the sticks that form a dual pair are the same size and preferably from the same manufacturer and you'll be fine
FYI the 27" iMac has 4 RAM slots for 2 channels.
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Old Nov 30, 2012, 12:35 PM   #11
Galatian
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FYI the 27" iMac has 4 RAM slots for 2 channels.
I know...not sure what your point is?
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Old Nov 30, 2012, 12:37 PM   #12
lixuelai
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I know...not sure what your point is?
Well it seemed like you didn't. I mentioned 12GB on each channel which means 12GB in 2 RAM slots. The math isn't hard after that
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Old Nov 30, 2012, 12:42 PM   #13
BSoares
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Just ordered from Crucial. I used ebates which has 6% cashback and a 5% off coupon, also used their 16GB kit that isn't the one they bring up when you select the iMac but it's the exact same specs (CT2KIT102464BF160B). So that kit with the coupon is $72.19 and you'll get 6% back in cashback if you use ebates. I know there was a better deal for G.Skill but I like Crucial better. Plan on adding the kit to have a total of 24GB.
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Old Nov 30, 2012, 12:46 PM   #14
Hesays
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Well it seemed like you didn't. I mentioned 12GB on each channel which means 12GB in 2 RAM slots. The math isn't hard after that
I'm honestly unsure on how this works. So is it better to have 8 and 4 in one channel and 8 and 4 in the other. Or 8 and 8 and 4 and 4 beside each other. Thoughts memory Gurus?
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Old Nov 30, 2012, 12:46 PM   #15
bflowers
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those of you pulling the original 8 should consider selling it cheap to someone here. with paypal or a similar service, you could make a safe transaction and not bother with the additional fees of ebay. The benefit over somewhere like Craigslist, your working with a fellow iMac owner
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Old Nov 30, 2012, 12:48 PM   #16
Galatian
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Well it seemed like you didn't. I mentioned 12GB on each channel which means 12GB in 2 RAM slots. The math isn't hard after that
No math seems to be hard for you: there are no 6 nor 12 nor 3 GB sticks out there. How could you put a 6 GB stick into one slot?
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Old Nov 30, 2012, 12:50 PM   #17
Hesays
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No math seems to be hard for you: there are no 6 nor 12 nor 3 GB sticks out there. How could you put a 6 GB stick into one slot?
He's talking about an 8gig and a 4 gig in one channel to make up the 12 he's referring to. My question is that the way you should do it. Or have same memory sizes to match the one going into the same channel.
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Old Nov 30, 2012, 12:50 PM   #18
lixuelai
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no math seems to be hard for you: There are no 6 nor 12 nor 3 gb sticks out there. How could you put a 6 gb stick into one slot?
-.-"

8 + 4 + 8 + 4 = 24.

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I'm honestly unsure on how this works. So is it better to have 8 and 4 in one channel and 8 and 4 in the other. Or 8 and 8 and 4 and 4 beside each other. Thoughts memory Gurus?
8 + 4 in each channel will give you dual channel. 8 + 8 in one and 4 + 4 in another will give you async dual channel which is a very small performance loss. Honestly it doesn't matter but if you want to be 100% sure you don't lose out on any performance just put 8 + 4 in each channel. I don't know the DIMM assignments for the new iMac but it is not hard to figure out once you get it (you have 50% chance of getting it right lol).
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Old Nov 30, 2012, 12:53 PM   #19
bflowers
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He's talking about an 8gig and a 4 gig in one channel to make up the 12 he's referring to. My question is that the way you should do it. Or have same memory sizes to match the one going into the same channel.
I would simply check with Apple on proper instillation. Might even be in the manual. it can't be that hard to figure out, as they will have installed the 2x4GB into slots to take advantage of the performance channels, leaving the two remaining for whatever you want to add.
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Old Nov 30, 2012, 12:54 PM   #20
Hesays
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8 + 4 in each channel will give you dual channel. 8 + 8 in one and 4 + 4 in another will give you async dual channel which is a very small performance loss. Honestly it doesn't matter but if you want to be 100% sure you don't lose out on any performance just put 8 + 4 in each channel. I don't know the DIMM assignments for the new iMac but it is not hard to figure out once you get it (you have 50% chance of getting it right lol).


Sweet! Much appreciated!
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Old Nov 30, 2012, 12:55 PM   #21
bflowers
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-.-"(you have 50% chance of getting it right lol).
probably less than 50%, as you have 4 DIMMs and 4 slots, with 2 types of DIMMs, but as I only got 4 hours of sleep waiting up to order my iMac, I'm not doing the probability in my head right now
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Old Nov 30, 2012, 12:56 PM   #22
Hesays
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probably less than 50%, as you have 4 DIMMs and 4 slots, with 2 types of DIMMs, but as I only got 4 hours of sleep waiting up to order my iMac, I'm not doing the probability in my head right now
Lolol. Cheers for the insight. Easier than I thought. I GOT NERVOUS OK
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Old Nov 30, 2012, 01:01 PM   #23
Foxer
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I came to ask this precise question. The consensus seems to be that, if you buy a 16GB kit (8x2) and put a stick in each empty slot, you'll be in sync and problem free. Right?
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Old Nov 30, 2012, 01:02 PM   #24
bflowers
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For the record, unless someone on here wants to sell me their spare 4GBx2 at a reasonable price, I will eventually buy a pair of 8GBs to jump to 24. However, as I get so few PageOuts on my three year old MacBook that I bumped to 8GB (exceeding Apple's Max of 6GB), I can afford to wait a few months.

Either way, may just jump on Apple's site and use the Chat to ask for an official upgrade answer...
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Old Nov 30, 2012, 01:06 PM   #25
lixuelai
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probably less than 50%, as you have 4 DIMMs and 4 slots, with 2 types of DIMMs, but as I only got 4 hours of sleep waiting up to order my iMac, I'm not doing the probability in my head right now
It will certainly be less than 50% just trying randomly. But in reality it will be either 8/4/8/4 or 8/8/4/4.

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I came to ask this precise question. The consensus seems to be that, if you buy a 16GB kit (8x2) and put a stick in each empty slot, you'll be in sync and problem free. Right?
Short answer is yes. You bring up a good point though. Apple undoubtedly installed the existing RAM in dual channel so if you buy a 16GB kit you are guaranteed to get dual channel unless you bought the wrong RAM.
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