There are different configurations of memory for Mac machines. When you buy mac memory, it is important to have some understanding of how to deal with these differences – from testing to upgrades and cleaning.
You will find a number of different ways you can test your memory, as well as other issues that might be troubling your Mac. One of those is the Apple Hardware Test, or AHT.
The AHT has a number of different tools in the diagnostic suite. They can help you determine whether you are having 
hardware issues or some other type of issue with your Mac. To start the test, you should turn on your computer and then press and hold the D key before the startup screen appears. This should start the AHT for you.
Just as you might be able to surmise from the name, Memtest is a test of your system’s memory. You will be able to use the test to determine how your memory is working and if you have any errors. The original test is called MemTest86, and was originally only for the PC. You can now find free downloads of Memtest you can download and use for the Mac operating system. After you download and install, you can launch the Terminal and type "memtest all 2" to get started.
To make things even easier, you will be able to add Rember, which is a user interface for Memtest. You will be able to choose the loops you want to test, and you will be able to choose how much memory to test. In addition, you will be able to limit the output.
If you do not have any problems with your memory, you will get a message that tells you “all tests passed” when the memory test completes. If you do have trouble, chances are that the system is going to start freezing on you when testing. This could mean you have a bad module, and you likely need to replace it.
