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Running The Apple Hardware Test

written by: Michael Dougherty•edited by: Christian Cawley•updated: 9/9/2010

The Apple Hardware Test began shipping with new Mac computers in the year 2000. If you suspect an issue with your hardware, you can run this test to determine the issue.

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    What Does The Apple Hardware Test Do?

    The Apple Hardware Test is a very special troubleshooting program that ships with every Mac. It performs a number of diagnostic tests on Mac hardware including RAM, video RAM, modem, AirPort card, hard drive and logic board. The test can also discover subtle hardware defects, which could lead to serious problems in the future. Whether your Mac is new or years old and you want to make sure that its main components are in healthy state, this is an easy method to do so.

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    Running The Apple Hardware Test

    The Apple Hardware Test comes in the Mac OS X Install Disc. To run the test, you must start your Mac from the volume or disc that contains the test.

    Running the test when you’ve an Apple Hardware Test CD:

    A. Insert the disc in Mac’s disc drive.

    B. Restart the Mac.

    C. Immediately press the C button on the keyboard and hold it down for a moment and the program will load.

    D. When the Apple Hardware Test shows up on your screen, release the C button.

    Running the test when you’ve a PowerPC-based Mac

    A. Insert the Mac OS X Install Disc # 1, which came with the Mac into the optical drive.

    B. Restart your Mac.

    C. Immediately press the Option button on your keyboard and hold for some seconds. This will invoke Mac’s Startup Manager.

    D. Once the Startup Manager opens, release the Option key. You will see the available startup volumes on the screen.

    E. Click on the Apple Hardware Test icon then click on the right arrow and the program will load.

    F. Select the Extended Test from the Hardware Tests tab to start the test.

    It is recommended you run this test several times as all the issues may not come up in just one test.

    If you have an Intel-based Mac, please see the instructions here. And if you have MacBook Air, visit this website for the instructions.

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    Running The Test in Loop Mode

    You can use the loop mode to run the test, which is an excellent way for detecting intermittent hardware issues. It is also very useful for finding irregular kernel panics.

    If the version of your Apple Hardware Test supports loop mode, you can run the Extended Test by pressing the Control-L shortcut before you start the test. You will see Looping On at the right side of the window. In the end, click the button labeled Extended Test.

    The test’ll continuously run if it doesn’t find a problem. On finding a problem, the test’ll stop. Sometimes, finding a problem may need many loops, so it is a good idea to run the test overnight. In case no problem is found after running the test overnight, you can exit the loop and stop the test by either pressing the Cmd – shortcut or clicking on the Stop Test or Cancel buttons.

    -- You might also want to learn how to run the Apple Hardware Test on a MacBook Air and how to run the Apple Hardware Test on Intel-based Macs.