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hakr100

macrumors 6502a
Original poster
Mar 1, 2011
967
113
East Coast
Got my new iMac last week with 8GB of ram, ordered another 8GB of Crucial from Amazon.

Memory arrived today. One strip of ram chips, 8GB. I thought ram had to be inserted in the iMac in pairs.

Inserted strip of ram, machine booted right up properly and reported everything A'OK, per attached screen shot.

So, memory does not have to be inserted in matched pairs? I am confused. :confused:
 

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DeltaMac

macrumors G5
Jul 30, 2003
13,422
4,391
Delaware
If you meant to order a pair of 4 GB chips, then you should have returned that single 8 GB for the pair that you really wanted.

But, no, most Macs don't require the RAM to be matched pairs.
You WILL measure somewhat better performance with a matched pair, but you would not likely notice any difference in real use.

And, now you know that each slot supports up to 8 GB, so you could add a second 8 GB chip to the open slot.
 

hakr100

macrumors 6502a
Original poster
Mar 1, 2011
967
113
East Coast
No, I just ordered the 8GB and got the one stick. I figured it would show up as two sticks. But it seems to work fine. Well, another day, another lesson learned!
:)
 

Chippy99

macrumors 6502a
Apr 28, 2012
989
35
One stick will work but will only work at half the speed. The CPU has a dual channel memory controller, so with only 1 stick loaded, it can only drive one channel and operates at half the possible speed. That's why you need to install it in pairs.
 

T'hain Esh Kelch

macrumors 603
Aug 5, 2001
6,311
7,152
Denmark
The old Mac Pro was required to have memory installed in pairs, and I assume the new one also requires it. I believe it is the only machine that has had that dependency.
 
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