Upgrading Memory on my 27 inc Imac

It is okay to use the stock 4 GB RAM and have 12 GB RAM.

ELtoro2010 said:

Hello everyone

I`am New to mac
so i bought a 27 Imac and its came out with 4 gig of ram.
yesterday i purchase an 8 gig ram from macsale.com my question is it o.k to keep the stock ram installed with the new ram or may it cause some problems?

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Yes, it may cause some problems. You'll just have to try it out. It is very likely to work well, but it may also lead to crashes. For example: I had a problem with Corsair RAM - when paired with original Apple Samsung RAM, my iMac was randomly crashing. I have removed the Samsung RAM and its stable even now. Other people reported stable machines with exactly the same Corsair RAM mix. So its a hit and miss case

There will be no issues.

As long as they are both the correct clock speeds and type of ram, you'll be fine. I've done the exact same thing with mine (upgraded from 4Gb to 12GB) and it runs like a dream.

ELtoro2010 said:

But the New one is (owc) and the Stock is (Samsung)

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I recently installed 8Gig of OWC memory with the stock 4GB Samsung in my mid-2011 27" iMac and it works great. No worries.

I just put another 8GB (2x4GB) of Corsair RAM in mine and it works fine with the OEM RAM, for a total of 12GB.

NOTE: I don't know why, but if you are going to install 2x4GB sticks and keep your OEM RAM, move the 2x2GB Samsung sticks down to the lower slots and install the new RAM in the top slots.

I read somewhere that it wouldn't POST if you didn't do it that way. I can't confirm this myself as I just did it when I install my Corsair RAM.

I recently added 8G of OWC ram to my mid2011 21.5 iMac along with the stock 4G and it seems to be working just fine. I too put the new RAM in the top slots and the stock RAM in the bottom. System recognized it right away and no problems so far.