With the arrival of Mac OS X Lion, a lot of folks are going to discover that Apple's latest operating system is more of a memory hog than Snow Leopard and that a little RAM boost may be required.
Regardless of whether you're upgrading to Lion or not, upgrading your RAM is good idea because it's one of the most affordable--and easiest--ways to speed up your machine. Also, for anybody looking to buy a new iMac, we strongly recommend upgrading the RAM yourself, because you can save a good bit of money by not ordering extra RAM from Apple when you initially buy your iMac.
For instance, to add an additional 8GB of RAM, Apple would charge you $200 while two 4GB modules of the Kingston memory that Kingston provided for the demo would run you around $70. Ridiculously, Apple charges $600 for a full 16GB upgrade, when you can do the same upgrade for less than a third of the cost.
Step 1: Find out what iMac you have
The first thing to do is figure out just what iMac you have. Check on Apple's Web site to figure out which model you have, what kind of RAM it takes, how much memory you can put in your machine. The last couple of years, the base configuration of the iMac has come with 4GB of RAM in two 2GB memory modules, which takes up two of the four memory slots in the iMac. What a lot of people do is keep the existing 2GB modules in place, then add an additional two 4G modules, bringing the total to 12GB. You can buy RAM at Macsales.com or sites like Newegg.com and Amazon.com.
To get to the memory compartment, lay your iMac on a soft surface (unplug it first, of course), with the screen facing down. Then, all you have to do is unscrew the three Phillips screws for the plate (Apple calls it a "door") that covers the compartment on the bottom of the iMac to gain access to your memory.
Step 3: Remove any unwanted memory modules
As you can see from the video, you'll have two slots open for additional memory. The iMac we used for the demo is a 2011 model, which accepts up to 16GB of RAM, as do the 2010 models. Alas, modules only go up to 4G, so if you want to get to the full 16GB, you have to replace your current 2GB modules with 4GB modules. To get an existing module or modules out, you pull on the plastic ribbon (it may require a good pull; don't be shy about it). The ribbon will pull out both the top and bottom modules at the same time, so you should remove any unwanted memory before you add new modules.
Step 4: Slide new memory modules into open slots
As we said, a lot of people choose to leave their existing 4GB of RAM in place and add another 8GB (2x4GB). To install a module, you simply slide it into an open compartment, push hard, and wait until you feel a little click that tells you it's snapped in place. Make sure you install the RAM with the stickers (labels) facing up. You can always look to see how any existing modules are installed to figure out which way the modules should face.
Now it's time to screw the memory access door back on and stand your computer back up. Once you plug it in and power it on, you can select "About this Mac" under the Apple logo in the top left of your screen and it should show that your new memory has been installed. You should also notice that the overall performance of your machine is zippier, especially when you open multiple applications or applications such as Photoshop that require a lot of memory. But even basic tasks like surfing the Web should feel faster.