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My MacMini, which I bought new around Thanksgiving 2010 from Amazon, has been having quite a few kernel panics. They aren't consistent in any way, but they have become more frequent and now many apps seem to be crashing more as well and I have also noticed Spotlight and Alfred have become painfully slow.

I was about to reinstall Snow Leopard and start from scratch after making a SuperDuper clone on an external for backup when I read on the Apple CD that you can run an "Apple Hardware Test" by holding "D" during startup.

I figured it was worth checking out. Especially since my memory is non-original. I had put 2x 4GB Corsair sticks in it right away that I also got from Amazon a few months before then which I had used in my previous early-2009 MacMini. The memory seemed to have worked fine in both computers. All 8 GB were being recognized. These kernel panics only started happening a few months ago.

Now the Apple Hardware tests, which I tried in every conceivable configuration; swapping slots, removing one then the other etc., did in fact show errors. I wrote down two of the error codes. I believe there were only two unique codes; I suppose the different stick arrangements I used is cause for the variances, but it's possible there were more, but I know for a fact they all started out with the same characters, 4MEM/9/40000000: .

4MEM/9/40000000: 0xa90c1418 & 4MEM/9/40000000: 0xa95de698

However, the strange thing is the Apple Hardware Test only showed this error when I had BOTH sticks installed; either stick in either slot on it's own showed no error. As I mentioned earlier, I tested all possible configurations because I had read that sometimes it could be a faulty slot.

So, with that information, does anyone have an idea how to fix my Mac. Do I need to replace one or both sticks? Is it something else? Is there an app I can use to help diagnose the issue?

As I'm writing, I realized I can still try using both the original sticks that came with the Mac at the same time, but I need to find them. I may wait until tomorrow to try that.

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3 Answers 3

Reset to default
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It sounds like some sort of RAM issue for sure, and there are a few memtest based programs out there to try and run and see if you run into problems. Rember is a gui based memtest, and applejack is a fairly well known utility script that also contains it.

I dont know why you only got the error with a specific configuration of ram, but with 8GB of addressable space it can take a while to find the bad guy.

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I agree with hobs. I recently had a similar problem - random KPs that didn't point to any single process. I tracked it down using Prime95. It has a stress test which according to their README indicates that any errors are almost certainly tied to a hardware problem. Swapping RAM and running the test I was able to confirm that my 3rd party RAM was bad. I should note, Apple's hardware test never found a problem, nor did I find one with memtest (but I probably gave up too soon).

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  • Man I forgot prime95, +1
    – ConstantineK
    Apr 28, 2011 at 16:11
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I found my old stock RAM that came with my Mac and swapped it out and the kernel panics and app crashing stopped. I used it for a few days just to be sure. Then I went back and stuck in only one of the third party 4GB sticks and within an hour I had a few app crashes and a kernel panic. Then I swapped it with the other third party 4GB stick and after a week of use, it seems to be in working condition fortunately.

So ultimately, the answer is the app crashing and kernel panics were definitely due to faulty RAM.

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