can I upgrade memory from 8gb to 12gb?

16.

It'll work fine with 12GB. Make sure you buy from a supplier that gives you a lifetime warranty and explicitly says that the memory they have supplied is suitable for your EXACT model of Mac. Two companies that provide this level of assurance are OWC and Crucial.

You would only be asking this question because you are reluctant to waste money. So, I'll risk some unsolicited advice, which is that If you are upgrading to improve performance, review a few of the threads with titles like 'Mac running slow' on these forums first. Unless you are doing something genuinely memory intensive, like video production or running virtual machines, poor performance is not usually lack of RAM. Use Activity Monitor to keep an eye on 'memory pressure'. More memory will only help if this is out of the green for significant periods.

C.

You're welcome.

No money is saved if it doesn't work. 😉

Notes:

1. Although the iMac (Late 2006) computers will accept up to a 2 GB SO-DIMM in each of the two memory slots, the iMac will only support 3 GB total memory.
2. The iMac (Late 2009), iMac (Mid 2010) and iMac (Mid 2011) have four SDRAM slots, each of which can accept a 2 GB or 4 GB SO-DIMM.
3. iMac (21.5-inch, Late 2012 and later) computers have no user installable SDRAM slots.
4. iMac (27-inch, Late 2012 and later) computers have four SDRAM slots, each of which can accept a 4 GB, or 8 GB SO-DIMM.

Are you sure?

AFAIK, the Mac in question has 4 slots, originally populated with two 4GB sticks so there should be 2 empty slots. Crucial sell a 4GB upgrade for this machine, which is exactly what the OP wanted.

C.

Yes.

So let's be clear. You are saying that not only is Crucial selling an upgrade to this machine that won't work:

But also Apple's own instructions:

iMac: How to remove or install memory - Apple Support

are wrong.. Seems a bit of a stretch, but perhaps you actually own the model in question and have actually tested a 3 * 4 GB and found it doesn't work and are reporting your personal experience.

Taking account of that possibility, my recommendation is still that the OP buys a single 4GB upgrade in the first instance, and if it doesn't work they can return it under warranty or buy a second 4GB stick to make up a pair. I hope that they will report back what actually happens.

C.

Test it yourself.

DIMM should be bought in pairs.

ckuan wrote:

You're welcome.

No money is saved if it doesn't work. 😉

But it will work with 12 or 16, your info is incorrect.

I stand corrected.😊