Memtest OS X - Essential Tool for Testing Your RAM

[ravenvii]

Memtest is an essential tool for testing your RAM. If you are experiencing kernel panics or freezes, your RAM should be one of your first suspects. Or if you've just upgraded your Mac's RAM, and want to ensure that it is all good before you sell the old RAM. Or you merely want to make sure your RAM is good, so that in the future you can eliminate it as the source of the problem.

Whatever your situation is, if you need to test your RAM, Memtest OS X is the best tool for the job for your Mac. Yes, there's Memtest86+ - I always use that for all the PCs I own. However, there's a bug in Memtest86+ where it could give false positives on EFI machines (which all Intel Macs are).

Memtest, by the way, is open source. So why, then, do you have to pay to download it? You have to pay to download both the binary and the source. I believe this violates the GPL, which Memtest OS X, and Memtest before it, are released under.

So I'm attaching Memtest right here in this thread. Now you can download it for free, without having to pay. Unfortunately, I don't have the source .

To start the program, simply start it in the Terminal. It is suggested, however, that you use it in Single-User Mode for best results.

To boot into Single-User Mode, hold command-S on boot.

Then type those commands:

/sbin/fsck -fy

/sbin/mount -uw /

The first command is a quick checkup of your HD. Not strictly necessary, but it only takes a few seconds, and is generally a good idea.

Once the HD is mounted, cd (change directory) to where the memtest program is located. For example, if you put memtest in your Applications folder, the path would be:

cd /Applications

Or if you put it in the Utilities folder, it would be

cd /Applications/Utilities

And so on. You get the idea.

Then you can run memtest with a simple "./memtest" command. However, there's stuff you can customize. The first is how much memory you want to test. I'd say all, so just put "all" after "./memtest". Then comes how many times you want to run the test. 3 to 5 are good numbers, so just put that number after "all". Then you can decide whether you want the results logged or not with a -L. There's more, but those are the basics, and all you need to know.

So a simple 3-round memtest test of all available memory would be:

./memtest all 3

That's it.

[Shownarou]

This sure looks an awful lot like an advertisement..

[ikermalli]

He's been here almost 5 years and has 4000+ posts and he is giving out the binary for it free. Doesn't seem like an advertisement.

Thanks for this, does this work with Snow Leopard?

[ravenvii]

Originally Posted by ikermalli

He's been here almost 5 years and has 4000+ posts and he is giving out the binary for it free. Doesn't seem like an advertisement.

Thanks for this, does this work with Snow Leopard?

Yep it does work perfectly under Snow Leopard. 64-bit mode and all.

[Shownarou]

Originally Posted by ikermalli

He's been here almost 5 years and has 4000+ posts and he is giving out the binary for it free. Doesn't seem like an advertisement.

Thanks for this, does this work with Snow Leopard?

Oh, okay I get it. Sorry about that OP. Thanks by the way!

[appleguru1]

Thanks for this!

This is the latest Memtest version 4.22 (64-bit) :-)

Though the developer's $1.39 fee is hardly unfair, and AFAICT is permitted per the GPL v2 that it is licensed under. I'm fairly certain he has to make the source available though..

[rpaloalto]

Thanks

[dukebound85]

i use rember
http://www.kelleycomputing.net/rember/

its a gui version of memtest and is free

[Ibjr]

Originally Posted by Shownarou

This sure looks an awful lot like an advertisement..

You're just too cool for school.

[Shownarou]

Originally Posted by Ibjr

You're just too cool for school.

Did you even read the rest of the thread?

[krunk]

Memtest, by the way, is open source. So why, then, do you have to pay to download it? You have to pay to download both the binary and the source. I believe this violates the GPL, which Memtest OS X, and Memtest before it, are released under.

Have you asked for the source from the author? If I understand the GPL correctly, you are not required to host the source. But you are required to provide the source if asked.

-james

[ravenvii]

Originally Posted by krunk

Have you asked for the source from the author? If I understand the GPL correctly, you are not required to host the source. But you are required to provide the source if asked.

-james

You are required to pay the money to download memtest to get the source. Which is why I went and put memtest up here for free. If the developer puts up the source without the download fee, then I would remove the download here, since the developer is acting within the GPL license. Since he is not, I decided to take things into my own hands

And re: Rember, memtest is better because you can use it in single-user mode, and hence memtest will be able to test more of your memory than Rember can (it couldn't test memory that's tied up by OS X, UI elements and programs running in the background).

[imom]

thanks to the OP!

[Silencio]

Memtest is also bundled with AppleJack. It provides a simplified user interface for running Memtest from Single User Mode, amongst numerous other useful maintenance and troubleshooting scripts. I install this on every Mac I look after.

http://applejack.sourceforge.net/

[balamw]

I picked up Applejack based on this thread. Thanks!

Only problem I have now is getting my Mac to boot into single user mode using the 64 bit kernel so I can test my 8 GB of RAM from OWC with the lock on.

EDIT: solved

nvram boot-args="arch=x86_64 -s"
reboot

B

[negatlov]

you have done a great job.

[graxspoo]

Hey, I'm having a weird problem with memtest. I just put 8 gigs in my new mac mini. Hit the "can't lock" issue with the 32 kernel mode, so figured out how to reboot in 64-bit kernel mode and single user mode. Ran memtest again, and it reported errors. After some swearing, I put the old memory back in, and, for another data point, rebooted into 64-bit kernel/single user mode and ran memtest again (now on the OEM memory) AGAIN errors reported. So, rebooted into 32 bit mode/single user, ran tests again NO ERRORS. Put the 8 gigs of memory back in, ran the tests again (32 bit/single user) NO ERRORS.

So in summery:
64 bit/single user mode: errors on both old and new memory
32 bit/single user mode: all tests pass on old and new memory

(in each case the command used was memtest all 3)

I'm beginning to think that memtest 4.22 can't be trusted in 64 bit kernel mode. Any advice? Does anyone have experience with memtest86+ what is the difference between that memory tester and memtest?
TIA

[peanutismint]

I may be doing something wrong here but I'm running Snow Leopard and don't seem to be getting far with Memtest in single user mode (I purchased the program before finding this thread!)....

'sbin/fsck -fy' gives me an '...is not recognized as an internal or external command...' error

'sbin/mount -uw' gives me 'unknown flag '-uw'


Am I doing something completely stupid here that I can't see?!

[rw3]

Has to be /sbin/fsck -fy

That first backslash is very important....

[chown33]

Originally Posted by rw3

Has to be /sbin/fsck -fy

That first backslash is very important....

I see no backslashes here. There are two slashes, though.

And if the working directory is / then "sbin/fsck" would work, but since the post is over 6 months old, it's probably too late to ask if he remembers what the working dir was.

[danpritts]

It is not a violation of the GPL to sell a derivative work. If it were, Apple would be in trouble for much of OS X (e.g., /bin/bash), which is also GPL licensed.

It *would* be a violation of the GPL to sell or otherwise distribute a derivative work, AND not distribute the source code with your changes.

Whether it is legal for you to distribute his derivative work (not the source code) is another question. I'm not sure but that might be illegal, if he claims copyright on the compiled binaries.

It would be legal to distribute his modified source, or to compile and distribute your own copy.

[ceet12]

hi thanks for the program and info, I'm about to install and use

but how would i go about uninstalling once finished?

Regards