how much RAM can you add to an IMAC 2011?

I have the same iMac (i7)...

All mid 2011 IMac's can take up to 32 GIGs of ram.

How do i be sure it is IMAC compatible if i buy from third party?

Use a vendor other Mac users have found reliable. For me it is this one:

http://eshop.macsales.com/shop/memory/iMac/2011/DDR3_21.5_27

I have bought all my Mac RAM from them for over a decade and can recommend them highly.

You can use the open slots to get from 4GB to:

<> 8 GB by adding two 2GB modules

<> 12GB by adding two 4G modules

<> 20GB by adding two 8GB module

without replacing the two modules now present. Other increments would require pulling the existing two and replacing them with bigger ones.

Regardless of the total amount, you will get best performance by pairing modules side by side in the slots. The slots will look like this when you remove the RAM door today:

[ 2GB ] [ 2GB ]

[ empty ] [ empty ]

This arrangement after adding two 4GB modules will give best performance:

[ 2GB ] [ 2GB ]

[ 4GB ] [ 4GB ]

This arrangement, although letting the computer work, is NOT considered optimum:

[ 2GB ] [ 4GB ]

[ 2GB ] [ 4GB ]

We don't know where you are located, The firm I linked is a US company but will ship to some, not all, international destinations. If you are not able to order from the place I linked, we'll need a rough idea of where you are to further help get you to a reliable RAM vendor.

I would recommend purchasing additional RAM from an Apple authorised service provider rather than any other third party.

Find a list of these on http://locate.apple.com, and give them a ring. They'll be able to point you in the right direction.

Also, check which RAM you are using/will need by clicking on the Apple logo and then clicking 'About this Mac' and information will be stored under 'Memory' e.g. "4GB 1600 MHz DDR3"

Apple RAM is far too expensive compared with the people usually recommended in these forums.

Many people on these forums speak well of the following memory suppliers.

In North America contact OWC … Upgrade Apple iMac Memory

In Europe contact Crucial.com … RAM Memory Upgrade

Both companies have facilities to guide you and will recommend the correct memory package to meet whatever needs you describe to them.

There may be benefits buying from whichever company has a branch in your own geographical location insofar as Shipping charges, Local sales taxes and Exchange rates. Check out the basic memory costs and do your sums.

Guide to required RAM. Lookup Mac Specs By Serial Number, Order, Model & EMC Number, Model ID @ EveryMac.com

I would recommend purchasing additional RAM from an Apple authorised service provider rather than any other third party.

Hi bad-wolf,

For many items, I will agree with you. However, for RAM those sources are commonly twice the cost of most suppliers. And an independent AASP may buy RAM from anywhere, not just Apple.

Even Apple uses multple vendors. I replaced RAM in a MacBook Pro and the factory-installed RAM was a brand I'd never heard of. I knew it was factory because it was my comptuer bought new directly from Apple.

Both OWC and Crucial have a long record of providing quality Mac RAM. I've never had a OWC module fail or otherwise act out in the decade+ I've been buying for the 17 Macs in our family or the Macs I maintain for friends and relatives.

One to avoid: Kingston Value RAM. Their standard RAM works fine in Macs but there have been a lot of reports here since Intel Macs came out of the Value version causing trouble that persisted until that RAM was replaced