Instructions for testing RAM


Introduction

The following article is intended to explain to you how you can test the system memory (RAM) of your PC correctly. I try to keep thing simple and understandable but that requires some explaining here and there. Don't be frightened by the text and take your time to read it.

Maybe you were pointed towards this article and don't really know why. Defective RAM can cause many different problems and whoever sent you here suspects that this might the case on your system. You should do the test. It cannot break anything and only costs some time.

We will use a program called MemTest86+ to test the RAM. I will explain to you in detail what you have to do. The program does not run under Windows because Windows protects the system memory from normal programs. Instead, MemTest86+ will boot directly from a CD (or another bootable device like an USB flash drive). You could say it comes with its own little operating system. But don't fear, it sounds more complicated than it is. And I even made pictures!

Before we begin, there are a few things you should know about RAM and its errors:
  • RAM can break spontaneously! It may have worked fine last week but that does not mean it can't be broken today.
  • RAM can also be defective right from the start. Even brand new memory modules can have errors.
  • In theory, there are standards that describe what manufacturers of RAM and mainboards have to do and every RAM module should work in every mainboard as long as they both use the same standard (something like "DDR3"). Unfortunately, this is not the case in the real world. It is common that specific memory modules cause errors in certain mainboards while they work fine in others. Many mainboard manufacturers publish so called "compatibility lists" in which they document with which memory modules they tested their products. If you give these lists a closer look, you'll see that sometimes even the amount of modules matters. Two modules of a certain kind may work fine while four of the same kind show errors. Or the other way around.
    This means: It does not matter if your RAM worked fine in another mainboard or in another combination. It can still cause memory faults now!
  • Memory faults may always show in the same way but they do not have to. Depending on what data is stored in the defective area at the moment, different problem will arise from its corruption. Lockups, freezes, crashes to desktop, blue screens, etc.
  • Some memory faults are not permanent and only triggered under certain circumstances. Temperature, voltage fluctuation, access pattern and a lot of other parameters can influence whether a weak memory cells manages to keep its data or whether it will loose it.
  • Because of that, it's possible that errors only appear in a certain game while others work fine - or crash so rarely that you do not pay any attention to it.
  • For that reason, we need to run the test for a longer period of time. A program like MemTest86+ cannot control all relevant parameters. "Real" memory testers are machines with the size of a closet and the price of a middle class car. Because we are only testing with "cheap" software, we have to keep testing and hope that the problematic factor combination will appear on its own.
    Hence, you should not abort MemTest86+ after the first successful pass. Let it run at least over night, better would be a whole day (24 h).
  • For the reasons above, MemTest86+ can never determine whether your memory modules are intact. It can only determine whether they are broken. If does not find anything that does not mean that there is nothing. It could just be difficult to trigger.
    Despite this fact, a memory test is advisable because if MemTest86+ finds errors then there is definitely something wrong with your RAM.



Required software

All programs that we will use are legally available for free in the internet. Go and get:
  • A program to extract ZIP archives. If you don't have one, you can use 7-Zip.
  • A program to burn CD recordables. In this text, I will refer to ImgBurn which is free of charge and easy to use. You can use a different burning application if you like, but don't expect any help from me if you don't know how to operate it.
    If you want to create a bootable flash drive, you do not need this program. But your mainboard must be able to boot from a flash drive which not all boards (especially older ones) can do.
  • The program MemTest86+. Go to the download site and grab the "Pre-Compiled Bootable ISO (.zip)":

    [Bild: memtest_download_en_2.jpg]


And you might want to get the manual for your mainboard. If you don't have a hardcopy, try the website of its manufacturer. It could prove useful later on if you are not familiar with the BIOS setup. If you don't know what mainboard you have, try running CPU-Z to get some info about it.

From now on, I will assume that the ZIP extraction program and ImgBurn are correctly installed.


Option 1: Create bootable flash drive

Extract the downloaded archive containing MemTest in a directory of your choice. I will use C:\ for simplicity. If you extract it somewhere else, you'll have to change the path names.
You should now have a file named Memtest86+ 4.10 USB Installer.exe. Maybe the file name was changed (i.e. increased version number) since this article was written but it should be an EXE file (type "application"). You do not need the original ZIP anymore.

Connect your flash drive to your PC and start the EXE file you just extracted by double clicking on it. On Windows 7 and Vista you may have to start it as administrator (via right click). Accept the license terms and choose the drive letter of you flash drive on the following screen. Also, check the box that reads "Check this box if you want to format the Drive.". Then click "Create".

[Bild: memtest_usb_installer.jpg]


Option 2: Burn MemTest to CD

Extract the downloaded archive containing MemTest in a directory of your choice. I will use C:\ for simplicity. If you extract it somewhere else, you'll have to change the path names.
You should now have a file named mt410.iso. Maybe the file name was changed (i.e. increased version number) since this article was written but it should be an ISO image file. Previously, the file was named memtest86+-4.00.iso. You do not need the original ZIP anymore.

Start ImgBurn. Two windows will pop up. One is just a log window. In the other window with the buttons, click on "Write image file to disc".

[Bild: imgburn-step001.jpg]

Now click on the little folder icon in the field "Source" and point to the file C:\memtest86+-4.00.iso. Below that, there should be a drop down list of available CD writers. Should you have more than one, choose the drive you wish to use and insert a blank CD recordable in it. You can safely reduce the burning speed to 4x or 8x. This will ensure an error-free writing process and the image is too small for the speed to actually matter. Finally, click on the large button in the lower left to start writing.

[Bild: imgburn_step002_en.jpg]



Boot MemTest86+

Once the writing is complete, you keep the flash drive connected or CD in the drive (or re-insert it if it got ejected). Now, reboot your PC.

In most cases, you computer should now boot from the CD or the flash drive we just created. If this does not happen and you see Windows again, it is likely that you have to tell you PC to boot from CD first.

There are two ways to tell your PC that you want it to boot from CD:
  • Most modern mainboard allow to call up a so called "boot menu" during the startup routine. With that menu, you can select a different boot device for this single instance and next time, the board will go back to the default. If your board provides such a boot menu, that would be the best way. Just call it up and select the drive with the MemTest CD or the flash drive in it.
    Usually, the key with which you can bring up the boot menu is displayed during the boot process (check the lower left or right). If not, it should be documented in the manual.
  • If your board does not have a boot menu, you will have to enter the BIOS setup and change the boot device priority. First CD/DVD or USB media, then hard drives. Unfortunately, there is no common standard where to find these options. Try "Boot", then "Boot priority order" or "Advanced BIOS Features" and then the settings for "First boot device", "Second boot device", and so on. Check the manual if you have doubts.
    You can bring up the BIOS setup during the boot process by pressing a key. The boot screen should tell you which one (check the lower left or right) but if not, this is also documented in the manual for your board.



The memory test itself

Now you should see MemTest86+ running. That looks like this:

[Bild: memtest86_screen_en.jpg]

Normally, you don't have to do anything here. MemTest86+ starts right away with its job and will continue running until you reboot the PC by pressing the ESC key or shutting it down.

Explanation: On the upper left you see a few general statistics to your board, your CPU and your RAM. The upper right displays details for the current test run. In the middle, you can see a summary of the diagnosis so far and below that, all errors that were encountered are listed.
Naturally, that lower half should remain empty. If your RAM is badly broken, it can be flooded with red error messages but even one single line after 9 hours is one line too much.

Important: Let MemTest86+ run for at least 12 hours, better 24 hours without interruption!

If errors show up you can abort. Then we know what we need to know. Otherwise, you have to keep testing for the reasons stated above.



MemTest finds errors. What now?

First of all, you should try something very simple: Turn off you PC and pull out the power cable from the outlet. Wait for 5 minutes, then plug it back in, restart your PC and repeat the memory test. In rare cases this can help to remove a "defect". It will most likely not help you but since it is so very easy, we should try it first.

Warning: Until now, everything was harmless and could not break anything. From this point forward, we will do things that can have grave consequences for your hardware if not done properly. If you have any doubts about this, I strongly suggest you do not continue and bring your PC to a professional!


Ok, so MemTest86+ found some errors. What can you do? First, you should check if you can set the parameters that your mainboard uses to operate your RAM modules to more conservative values. Some RAM does not like it when you try to overclock it or use aggressive timing parameters. But if you use slower settings, it might work without problems.

Again, there's no common rule where these settings are located in the BIOS setup and I have to point you to the manual of your mainboard. Some BIOS setups have a function called "Load Safe Defaults" on the first page. If you have something like that, it's always worth a try. Don't forget to reactivate the RAID or AHCI mode for your hard drives if you used it before - otherwise you might encounter data loss.
If you don't have such a function, you'll have to tweak the parameters manually but you should only try that if you know what you're doing.

Once the parameters are reduced, you have to repeat the test and see if it helped.

If it does not help or you don't want to play with the memory parameters, you can try to open your PC. If there are more than one memory modules installed, remove all but one. Repeat the memory test for all modules by testing them one by one without the others. If you're lucky, only one module is broken and the rest will work problem-free. If you have different modules from different manufacturers, restrict yourself to a single variety combination. Never mix different modules.

If that does not help either, you're bound to buy new memory. Check if your mainboard manufacturer publishes a compatibility list and try to stick to modules that are recommended for your board.