How to Check Your Mac's Memory for Problems – MUO – MakeUseOf


Wondering how to check the memory on your Mac? Here’s how to test your RAM to see how much you have and learn if it’s faulty.
Random Access Memory (RAM) is a vital component of any computer. When you launch an app on your Mac, it requires a portion of your available memory to run. Serious problems can arise if there are problems with your computer's memory.
In this tutorial, we'll look at how to find out how much memory you have in your Mac, what's using it, and how you can perform thorough testing to ensure it's working correctly. If you recently installed a new stick of RAM and you're encountering problems, performing a Mac memory test is a vital part of troubleshooting the issue.
To find out how much memory your Mac has, click on the Apple logo in the top-left corner of your screen and select About This Mac. On the Overview tab, the Memory line lists the amount of RAM in GB, the speed of the RAM in MHz, and the generation of double data rate (DDR) you're currently using.
This is important if you intend to add more RAM to your Mac, since you'll want to match any RAM you install with your existing RAM. This is mostly advice for owners of iMacs and older MacBooks, since the RAM on Apple's newer laptops is soldered to the logic board and not upgradeable.
Also, if you use an Apple silicon Mac with unified memory, you won't see any details except for the total amount of RAM.
Click System Report and navigate to the Memory section to find out even more information. Here you can see how many sticks of RAM you have installed, which is another important piece of information to keep in mind if you want to upgrade. macOS will also give you a status report of your memory's current condition (though you'll need further testing to isolate problems).
Activity Monitor is a small app that lives in the Applications > Utilities folder. It provides information about what's currently running on your machine. You can also use it to find out which apps are using your available memory, and how much they're using.
Launch Activity Monitor and click on the Memory tab. Then, sort the Memory column by descending order (meaning it will show a downwards pointing arrow) to see processes that are using the most memory at the top. Don't worry if you see "kernel_task" using a lot of memory, that's usually just the operating system ticking along in the background.
You can kill any process by selecting it and clicking on the X button at the top of the window. Keep in mind that this will close the corresponding app or browser tab. To avoid data loss, quit the application as you normally would instead, or by selecting it and using the Cmd + Q shortcut.
At the bottom of this screen, you'll see a summary of your Mac's total memory, the amount you're currently using, and a graph showing memory "pressure" over time. Try opening a few apps to see how they affect performance.
There are a few telltale signs that suggest your memory may not be working correctly. Watch out for any of these problems:
The best way to check your Mac's memory for problems is to perform memory testing while using as little of it as possible. Since the operating system uses quite a bit of RAM in the background, testing memory by booting into a lightweight testing environment is recommended.
There are two methods to conduct a Mac RAM test that we'll look at today: Apple's own set of user diagnostics and a third-party utility called MemTest86.
Testing your RAM with Apple's user diagnostics tools is easy. Simply restart your Mac, and then hold down D as soon as it restarts. If you did it correctly, your computer will either boot into Apple Diagnostics or Apple Hardware Test, depending on the age of your machine.
Apple silicon Macs require a different way of entering Apple Diagnostics. You must first shut the Mac down and turn it back on, holding down the Power button until you get to the startup options screen. Then, press Cmd + D.
Follow the prompts and let the test complete. It can take a while, particularly on older computers. When you're done, you should see a report giving you a brief overview of any detected issues. Unfortunately, the test will only tell you whether or not problems were detected. You won't be able to tell which stick of RAM is faulty.
Problems running the test? Holding down Option + D at startup will run this test from the internet. It will take longer to gather the required files, but it should work just as well once the download completes. This only applies to Intel Macs.
If you want to learn more about any problems Apple's diagnostics detected, or you want to run another test for peace of mind, MemTest86 is one of the best tools for the job. There are a few memory testing tools that use similar names, but MemTest86 is still regularly maintained and updated.
Unfortunately, MemTest86 requires UEFI firmware, so don't expect it to run on Macs with Apple silicon.
In order to test your machine, you're going to need to make a bootable USB drive from which to run the test. The first step is to find a suitable USB drive and make sure there are no important files on there, since the whole drive will be erased. Then, insert the USB drive into a free port.
Now download the free drive creation tool Etcher, mount the DMG, and install it to your Applications folder. Then, head to the MemTest86 Downloads page and grab the Image for creating bootable USB Drive under Linux/Mac Downloads.
Once MemTest86 has downloaded, extract the archive and launch Etcher. Then click Select image, navigate to the extracted archive you previously downloaded, and choose the memtest-usb.img file. Now click Select drive and choose the USB drive you want to use. When you're ready, click Flash! and wait for the process to complete.
Next, shut down the Mac you want to test and insert the USB drive you just created. Press and hold the Option key and power on your Mac. When prompted, select the external drive you created (it may show up as EFI Boot) by clicking the arrow to boot into MemTest86. Don't select Macintosh HD, since this is your internal drive.
Wait for MemTest86 to initialize. Testing should begin after a short pause, but if it doesn't, select Config > Start Test. Allow time for the test to complete; it took around 40 minutes on our test machine. At the end, you'll be given a summary and an option to save a report to the USB drive in HTML format.
Save the report if you find anything unusual and use it to seek help on message boards like Apple Support Communities or from a computer technician.
Note: If you use an Intel Mac with an Apple T2 Security Chip, you may have to enable booting from external media before you can run MemTest86. To do that, hold down the Cmd + R keys and restart the device to load macOS Recovery. Then, select Utilities > Startup Security Utility on the menu bar and activate the Allow booting from external or removable media setting.
Related: A Complete Guide to macOS Recovery
Some people use "memory" as a catch-all term for free space, but macOS specifically refers to this as "storage." You can find more information about this by clicking the Apple logo, selecting About This Mac, then clicking on the Storage tab. If you're close to running out of storage, learn how to create as much free space as possible.
Tim is a freelance writer who lives in Melbourne, Australia. You can follow him on Twitter.
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