Mac: Find the memory issues with Apple Hardware Test

By | April 5, 2021

Comment: This is an old post that works for older Macs.

If your Mac hangs or behaves strangely, there is reason to suspect internal memory problems. That was the case when I was going to export the master to my wife’s latest children’s album. But the diagnosis may be closer than you might think. Via Apple support, I found out that the Mac has a built-in diagnostic program, called the Apple Hardware Test, which can find memory problems and which the other built-in tools cannot find. The program is by no means a novelty, but on the other hand not all Macs have the program anymore. I found a solution to what I share today further down. But first, the basics.


  1. Make sure your computer is connected to the internet. Then turn it off.

  2. Turn on the computer.

  3. Press the D button directly before the gray screen appears. It may take some time for the program to start, which is normal. If you have a new Mac that was shipped with OS X 10.7 Lion, AHT will be launched online, unless the hard drive contains it.

  4. Choose a language. After that, the program will do a first basic inspection before you can start the test itself.

  5. Choose whether you want to do a simple test, or a more detailed run-through. In the latter case, make sure the check box for this is selected. Click the Test button. And be prepared that it will take a good while!


In some cases, AHT is not installed on the hard disk and the Mac cannot boot AHT from the Internet. That was the case with my Macbook Pro, purchased in the spring of 2011 and which came with Snow Leopard – where AHT worked. When upgrading to Lion – which was included – I did a clean installation. And AHT will stop working. Since the computer was not shipped with Lion, it also does not have the right to start AHT via Apple’s servers.

Solution (OS X 10.5.5 or later):

  1. Locate your operating system installation discs that came with your computer.

  2. Insert disc 2, ie Application Install DVD. Also make sure that the contents of the disc are displayed in the Finder.

  3. With this content in focus, go to the Finder menu and select Go > Go to folder.

  4. Enter “Install“straight up and down, without any slashes or dashes, and press enter. The Packages folder should now appear. Enter it.

  5. Launch the file CPU_AHT.pkg and have the package installed.

Clear! You can now restart your computer with the D key pressed and access the Apple Hardware Test.