I know there is MemTest86+ for PCs, but what can I use to see if my RAM is actually good in an Apple product? Whether it's a MacBook, MacBook Pro, iMac or Mac Pro? What symptoms would show that RAM is bad?

  • If you have bad RAM, your computer probably won't boot successfully. Sep 12, 2011 at 23:34
  • I had an iMac G5 that booted for months with bad ram. The symptom I saw was infrequent (but more than I was used to) kernel panics. I finally associated the panics with my having installed a memory upgrade. (I can be slow). Confirmed bad module (using Rember), swapped with vendor, never saw another panic—or not so as I remember,
    – jaberg
    Jan 25, 2012 at 18:48

5 Answers 5


I've had bad RAM that still allowed the machine to boot - a stick of memory in my Mac Pro apparently failed gracefully overnight.

The first step would be to check system profiler to see if the memory is being recognized. If indeed it is, there's a version of MemTest for OS X: http://osxdaily.com/2011/05/03/memtest-mac-ram-test/


Kernel panics, the black screen & beeps (referenced elsewhere), or weird crashes that you can't attribute to anything else all can be caused by bad RAM.

I use Rember which provides a GUI interface to Memtest. It was suggested to me by a tech support rep at One World Computing as their approved way of checking for a bad module before returning ram for exchange. I didn't want to waste their time and resources if my problem, periodic kernel panics, wasn't, as I suspected, caused by a memory upgrade. It turned out that the memory was to blame.

Memtest and Rember will sometimes find problems that Apple's Hardware Test won't and I highly recommend using one of them if you're looking for bad memory modules.


Some signs of bad RAM also include black screen 3 beeps in 5 seconds, this may happen continuously, You can use the method that EpiGrad mentioned or alternatively you can test it with Apple's Hardware Test, if you still have the OSX Disc, insert disc, hold down d on start up memory test should be one of the main categories listed, unless it has been updated since i last used it.


It's not as exhaustive as MemTest and Rember, but there's a userspace utility called memtester. You can call it by using memtester 4G. Call memtester to see other options as well.

You should also be able to call memtest86 from a LiveCD for Ubuntu or most other operating systems. Give it a try.


I would highly recommend using memtest. It's a proven tool and often catches things that the built-in macOS tools will not. It's also worth noting that for best results, you should probably run it single-user mode. Test as much available memory as the program will let you, and run a few loops to be sure.

If you relied on the Rember UI for memtest in the past (the developers haven't updated it in 7+ years), I've written a UI for memtest just like rember, but built for the modern cocoa runtime (rember uses a ton of deprecated macOS). It's free and open source, available here: https://memoria.vsanthanam.com

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