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Testing computer memory for defects with memtest86+

Hardware Diagnostics - Part 1

Computer memory (RAM) is generally very reliable, as long as you don't abuse it (extreme overclocking, over-voltaging, overheating, static discharges or physical abuse), it will likely last decades.
RAM installed on a motherboard
There are a few situations though, when you really should test the memory of your computer, to make sure it's working reliably.
It's a good idea to test the memory any time you first install new memory, when you just bought a new computer, or when you do a memory upgrade.
Also when you change any memory related settings in the BIOS (that includes overclocking), or change the CPU of your computer (especially if the bus speed of the new CPU is different than the old one), it's advisable to do a memory test.
Last but not least, if you are experiencing instability, random lock-ups or crashes of your computer, the cause could be memory related.

A common free tool to do a thorough memory check is Memtest86+, it can be used as a standalone bootable CD (or USB memory stick or even floppy), or it can be installed in Linux in such a way, that it appears as additional boot option on the Lilo or Grub boot menu.

To install the Memtest86+ package in Mandriva Linux just type the following command as root:
 urpmi memtest86+ 
To use it, you need to reboot your computer, as Memtest86+ is a standalone bootable Linux kernel based application. At the Grub (or Lilo) boot menu just chose "Memory Test".

If you would rather use the bootable CD version, then download the ISO image from the Memtest86+ web site, burn it to CD and afterwards boot your computer off it.

Memtest86+ will start running automatically as soon as it has booted. While Memtest86+ is running, you can't do anything else with your computer. A complete memory test will take several hours and in some cases up to a day or more, depending on the amount of memory you have installed and the speed of your computer.

screenshot of Memtest86+ in action
screenshot of Memtest86+ in action

Should Memtest86+ report any errors, there could be several causes for this: incorrect BIOS settings, memory modules not seated properly or not 100% compatible with your motherboard or cpu, or you could have a defective memory module.

At this point you will have to proceed by trial and error, but before you attempt any of the following, make sure you read the warnings at the bottom of this article first!

You could set all BIOS settings to the safest values (often BIOSes have an option to set everything to safe default values, so you don't have to set each value individually).

If you have more than one memory module, you could remove all but one (providing your motherboard can run with only one memory module, some require a pair as a minimum and very old motherboards needed groups of four) and test each memory module, in turns, on it's own.

If the computer or the memory modules (if you bought them separately) are still under warranty and Memtest86+ persistently reports errors, even after you have tried safe BIOS settings, I would contact the vendor and report the memory as likely defective.
If you have more than one memory module and you have identified a single one with errors, then you only need to replace that module.
If at all possible, get a replacement module of the same make and type as the other modules you have, mixing different memory types in the same computer is not recommended, as it can cause problems.

  • always disconnect the mains power cable from your computer before adding or removing any memory modules, switching the computer off is not enough!
  • memory modules are very sensitive to static electricity, never touch the metal contacts on them!
  • don't bend them or use excessive force, when inserting them into the brackets on the motherboard.
  • before changing any BIOS settings, write down the current settings, so you can restore them if necessary.
  • read the BIOS/motherboard manuals first, before doing any changes.
  • if in doubt, always consult an expert, better be safe than sorry.

Memtest86+ home page:

Wikipedia Memtest86 page: forum, if you are a Linux user (not just Mandriva), you can post on this friendly forum to ask for related help:

[03-Feb-2009 - art-hw_diagnostics-pt1]