RAM install - 2x2gb + 2x4gb possible?

d82k

macrumors member
Original poster
Aug 24, 2011
47
0
Dear all,

I would like to add 8Gb ram memory to my iMac 27", it actually has 2x2Gb DDR3 1333 MHz modules.

I got the Kingston 8GB 1600MHz DDR3 Non-ECC CL9 SODIMM (http://www.ec.kingston.com/ecom/con...oot=en&LinkBack=&ktcpartno=KHX1600C9S3P1K2/8G)

I would like to know if is possible to install these 8gb in addition to the 4 already installed by default.
I have read that in order to have best performances modules should be installed in a certain way i.e.: equal size modules should be placed both on the same bank or both on the same dimm depending on the architecture of the computer.
Where i can find specific information about iMac?

Any suggestion advice?
Thank you for your help.
dk
 
Nov 28, 2010
22,670
28
located
Yes, that is possible. Using the same sticks (four 4 GB sticks) will give you just a bit more performance (10 to 20 %).
http://www.everyma.com is a good source to find specs.



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d82k

macrumors member
Original poster
Aug 24, 2011
47
0
Thank you simsaladimbamba for your reply.
I thought there was a specific order on how to put different ram modules in order to get best performances...
I just plugged the new two in the bottom block and it seems working.

dk
 

The-Pro

macrumors 65816
Dec 2, 2010
1,449
37
Germany
It'l work yes.
Just want to add that the premium you paid for the 1600MHz RAM was a waste of money if you keep the old 1333MHz RAM sticks inside aswell. This is because the new sticks wont run at 1600 MHz but at the 1333 of the others. All RAM sticks will run at the same speed.
 

d82k

macrumors member
Original poster
Aug 24, 2011
47
0
Thank you The-Pro.

I saw it in fact inside the memory information of the mac. hum.. so i should make some test to understand if it's better, in terms of performances, to have 12gb at 1333 or 8gb at 1600..
Thank you
dk
 

Binarymix

macrumors 65816
Nov 1, 2007
1,100
335
AFAIK the newer iMacs only support up to 1333Mhz.

So either way you're wasting money. Even if the 1600Mhz module works, it'll be throttled to 1333Mhz.
 

philipma1957

macrumors 603
Apr 13, 2010
6,309
213
Howell, New Jersey
Nope, like all sandy bridge CPU's they support up to 1866MHz
well it is true for quad core mac mini I have 2 sticks of 1600 ram and they run at 1600 .

as for what is better 4 sticks of 1600 gb.
mixing ram the way the op did is a waste of money and is asking for kernel problems.
the op is mixing;

size 2gb vs 4gb sticks

speed 1333 vs 1600 and

most likely chips are elipda vs samsung.

that is not the best idea.

I had a 2009 iMac and you could mix size 2gb vs 4gb and you could mix speed 1066 vs 1333 but when you did both random freezes occurred.


12gb mixed will run faster if you need 8 to 11gb ram. most users would need that much ram if running vm fusion.

8gb 1600 ram would be quicker if you ran 7gb or less ram.

the cheapest way to test is put in just the 2 sticks of 1600 ram and monitor your memory with activity monitor.

if you get very few page outs just run your machine with the 2 sticks of 1600 ram. if you get lots of page outs run your machine with the 12gb and see if the page outs lesson
 
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