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iMac RAM upgrade: Here's an affordable way to improve multitasking

Adding more RAM to your iMac is an easy way to give your computer more multitasking juice. Look out, open Chrome browser tabs!

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Apple has made upgrading the RAM ridiculously easy on 27-inch iMacs.

Patrick Holland/CNET

When you buy a new iMac from Apple, it can be costly to upgrade the RAM. For example, upgrading a new iMac from 8GB of RAM to 32GB will cost you an extra $600 through Apple's website. However, you have a much more wallet-friendly way to add RAM to an iMac: Do it yourself. Third-party sites like Other World Computing, aka OWC, and Crucial sell the same amount of RAM for around $150. That's a savings of $450. All you need to do is install it, which Apple has made relatively easy.

Even if you aren't buying a new iMac, upgrading the RAM on your old computer is a quick and affordable way to give your computer more multitasking juice to handle all of those open tabs in your Chrome browser.

Watch a step-by-step video below of the entire process from figuring out what iMac model you have to installing the actual RAM modules.

27-inch iMac vs. 21.5-inch iMac RAM access

iMacs come in two sizes -- 27-inch and 21.5-inch models. Since late 2012, 27-inch models have a door behind the stand that gives you easy access so you can add more RAM. If you have a pre-2011 27-inch or a 21.5-inch iMac, there's an access panel in the bottom grille of the computer.

Unfortunately, if you have a 21.5-inch model made after 2011 or an iMac Pro ($4,999 at Apple), there isn't a way to easily access RAM. Instead, you have to take apart most of the iMac to add more.

Identify your iMac model and max amount of RAM

Before you can install new RAM, you need to determine what kind of iMac you have. Look for either the year your computer came out or the model number. To do this:

1. Go to the Apple menu.

2. Select About This Mac.

3. Find the year your iMac was released. For example, mine is: iMac (27-inch, late 2013).

4. Also, look at the memory line to see how much RAM your computer already has.

5. Depending on which version of MacOS your computer is running, there may be a Memory tab you can click to view how much RAM you have and how many slots it's occupying. 

To find the model number, go back to the main About This Mac tab and click the System Report button. A hardware overview screen will appear. Go to the line that has the model identifier. In this case, mine is iMac14,2.

To find out the maximum amount of RAM your iMac can handle, check out this Apple Support page. Most iMacs from the past eight years can handle 32GB of RAM, and some can go as high as 128GB. A new iMac Pro can top out at 512GB.

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Where to buy iMac RAM and how much

Now that you're armed with more knowledge about your computer, you need to find a place to buy RAM. There are many vendors, but I highly recommend OWC and Crucial. RAM prices are competitive between the two sites but can fluctuate. Also for this article, Crucial provided us with the RAM.

Both sites can help you find the correct type of RAM for your machine. Probably the biggest choice you'll have to make is how much to add. For example, my 2013 iMac came with 8GB of RAM (two sticks of 4GB). The computer has four slots, with two of them filled. I could just buy two 8GB modules of (16GB total) and add them to the two empty slots. That would bring my iMac from 8GB of RAM to a total of 24GB.

Instead, I opted to remove those two sticks of 4GB RAM that came with my iMac and put in four sticks of 8GB RAM for a total of 32GB, the maximum supported on my iMac. But the choice really comes down to how old your computer is and how you use it. One advantage of upgrading RAM on an older iMac is that it's relatively affordable. Adding 16GB of RAM will cost you around $80.

I recommend installing RAM in pairs. For example, add two modules of 8GB of RAM instead of a single module of 16GB of RAM. It's not so much about cost savings, as it is a performance consideration.  Intel supports dual-channel architecture, which is optimized for memory in pairs. That said, it's not entirely clear how much of a performance hit your computer would take if you just installed a single stick of RAM.

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The installation process is straightforward.

Patrick Holland/CNET

Installing RAM in a 27-inch iMac

Once you have your RAM and are ready to install, shut down your iMac and give it time to cool off.

1. Disconnect the power cord and any other cables connected to your iMac.

2. Place a soft, clean towel on a flat surface to prevent scratching the screen.

3. Holding the sides, lay the computer slowly face down on the towel.

4. Find the small gray button in the power port and press it to open the memory compartment door. I used a spudger tool to get a little more purchase.

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The button to open the RAM door is in the circular indent where the power cable goes.

Patrick Holland/CNET

5. The button raises the edge of the door. So keep it depressed until you can remove the compartment door completely. Once off, set the door off to the side. The inside of the door has a diagram that shows how the RAM pop-up mechanism works and which way the RAM modules fit in.

6. Locate the two levers on the right and left side and push them outward to release the memory cage.

7. Pull the memory cage levers toward you, to lift the cage for easier access.

8. If you are removing the existing RAM from your iMac, pull the module straight up and out. Note the location of the notch on the bottom of the RAM so that you can orient the new RAM correctly. Depending on which iMac you have, the RAM notch might need to be oriented on the left or right. I'm installing RAM on a 27-inch, late-2013 iMac, so for me the notch needs to be on the right side.

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RAM modules have a notch on the bottom. Depending on your iMac model the notch will either go in on the right or left.

Patrick Holland/CNET

9. Install the new RAM by orienting the notch the correct way, setting it down in the slot and pressing firmly until you feel and hear it click into the slot. If you're installing only two new sticks of RAM place them in spaced apart. For example, use the first and third slot or the second and fourth slots.

10. Once all your RAM is installed, put the door back on, stand your iMac upright and plug it back in.

11. Turn your Mac on and go to the Apple menu.

12. Select About This Mac.

13. Look at the memory line or memory tab to make sure your new RAM shows up. 

Troubleshooting tones and RAM that doesn't show up

Depending on how old your iMac is you might hear a tone after you restart it. After installing RAM, iMacs from before 2017 might make a warning sound when you first start them up. If you hear one tone repeating every 5 seconds it means that no RAM is installed. In that case, double-check your installed RAM and make sure it's properly seated in its slot.

If you hear three successive tones, repeating with a 5-second pause in between, it means that the RAM you installed didn't pass a data integrity check. If that happens, double-check that the memory you installed is actually compatible with your model of iMac and try reseating the memory. If your Mac continues to make the tone, then it's time for a Genius Bar appointment.

For more about Macs, check out our review of MacOS Catalina and all the games you can play on Apple Arcade

Originally published earlier this week.