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What is the point of memtest?

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Why do people even bother to run memtest? I've found myself and heard reported by many others that their memory will pass memtest with flying colors and then behave terribly in windows. I've never heard anyone offer up an explaination for this, or what it might indicate about the memory being tested. At any rate, if memtest doesn't always catch the errors, why not use something like Super Pi, etc that pretty much always catches them?

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For me:


I've always used memtest to find my memories highest stable point. Now that doesn't necessarily mean it will remain the highest point once I bring the CPU back into the equation, but it has always given me a good standing point to start off on as far as memory max goes.

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Basically memtest can be used to make sure the memory is stable running at those speeds/timings/settings/voltages.


It does not strees the CPU out at all - unlike Windows which certainly does. It does test the CPU's memory controller which is needed to find the highest stable FSB your RAM can run at. I use it to tweak timings and settings till I can OC to the max.


As sais above: this is independent of the CPU which may or may not be able to be loaded up at the same high FSB as the memory (I know mine can't :() :)

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What is memtest?

Memtest is a program that can check the memory for errors.


How does it work? (general idea)

The program writes patterns to a memory location, 00001111.

It then reads the data that has just be sent to that location.

If there is a problem with the memory it may return a totally different pattern, 00001110.


So the program reports an error.


There are a few reasons why this may have happened

  • The memory is faulty, transistor in the chip is damaged or bad soldering on the module, could be anything.
  • The memory is not getting enough voltage, usually you can adjust the voltage setting in the motherboard's BIOS.
  • A bad power supply/too weak power supply is being used.
  • The PC has more than 1 memory module installed and they are not the same make/model/Revision, never mix unless you know they are exactly the same.
  • The memory settings in the BIOS are wrong, something may be overclocking the modules or the timings being used are wrong.
  • The memory/PC is getting too hot - make sure everything is being cooled or you have good airflow in your case.

When should I run memtest?

When you build a new PC you should always run memtest.


If you have never used memtest then you should run it as you may have a problem with your memory modules, are you getting any bluescreens or random restarts?


How long should I run memtest?

You should run memtest for a minimum of 3 hours, if you are getting errors instantly then its is quite clear that there is a problem somewhere.


To be absolutely sure that the memory is fine you should run memtest overnight or 8 hours.


And finally, 1 error is unacceptable. If program in windows accesses that memory location it will give you a bluescreen or restart the PC




Now this is a very useful program, I am sure many people who have used it and have had erroros on their modules will tell you, like me :)


Why memtest shows no errors but windows crashes


- A weak power supply will be more unstable in the OS environment, and can allow memtest to pass.


- Windows is corrupt or there is a driver issue.


- BIOS settings/Timings - in the OS more chipset features are active.


- Bad IDE controller/Sound device/SATA device, cd drives/ hard drives.


- A corrupt pagefile/no pagefile.

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Nice explanation.


I'll also add that you spare all the boot time into windows to test your settings.


The methodology can vary though : Personally I run a few (5-10) passes of test 8 before giving two more Mhz to the RAM. Every 20 Mhz (if everything's fine) I run a longer test (30 * test5, 20 * test 8) to deeper check stability, and I boot into windows and run Sandra. This way I go high quickly, and know the behaviour of my RAM. Finally a night test when it's time to sleep gives me very stable references points.


So when I flash a bios or changes some parameters, I know exactly what I had and what I get, thus knowing which is the best.



it would be nice to have also a CPUTest, stressing the CPU, without windows boot...

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Yuppers....everything everyone has already stated. Memtest is a great tool once you get a feel for how to use.


I'm playing with PQI's right now. One in slot one is memtest stable up to 245. Left it there for 7+ hours looping all tests. Dropped to 235 and put's it's brother in slot three and got a couple hundred errors. Switched slots and no errors, now I'm slowly climbing back up with both sticks at 238 right now. It's great for identifying little things like which module performs best in which dimm slot and establishing a max for yer memory. No point trying to run 250mhz in windows when yer memory aint cuttin' it at 245 in memtest ;)

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Everything they said above, and I will add I am using it to burn in my new memory. Anyone who does a burn-in is hoping to achieve higher memory FSB clocks and/or tighter memory timings.


The fact that you can pass memtest and still have windows errors is actually a good thing (kinda). It means you KNOW that the memory is not the issue! So, you can trouble shoot somewhere else. After you eliminate each component one by one, you can find the item causing the crash.



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