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My computer hangs at random on multiple occasions and on different OSes today, requiring me to hit the reset button. I suspect it could be a memory problem and did a memtest with memtest86.

It went through two passes with no errors. Is that enough, or do I need to run through overnight until I see an error?

What if it is a motherboard or CPU issue? How do I know without getting a new motherboard?

System Specifications:

  • Memory: 2.0GiB
  • Processor Pentium(R) Dual-Core CPU E5300 @ 2.60GHz x 2
  • Motherboard: ASUS P5KPL-AM EPU
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To help troubleshooting in general, could you post your system specs? – Marcus Chan Feb 7 '13 at 9:58
@MarcusChan, is that sufficient? – Question Overflow Feb 7 '13 at 10:05
Once is actually sufficient – Ramhound Feb 7 '13 at 12:09
You've probably gotten this figured out by now, but next time take a look at the kernel log on Linux after it hangs. That will give you an idea of what is going on. – scottkosty Jul 16 '14 at 15:24

I've run memtest and seen 6 passes with no errors, with 4+ errors per pass after that. I normally just run 3-4 passes, but it's certainly possible to miss errors by doing just a couple of passes. I'd imagine that some errors only pop up as the memory modules heat up, thus causing problems with memory running at a high voltage.

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+1; Thats what I experienced too so far. – Stefan K. Dec 8 '14 at 14:24
if it is a heat related problem wouldn't prime95 be a better test vector, to generate a lot more heat in the system? – Jeff Atwood Nov 6 '15 at 1:27
@JeffAtwood No expert here, but prime95 woudn't necessarily point to RAM errors right? – Hele Nov 18 '15 at 15:12
To test for heat related errors, run one instance of memtest per CPU core.Select your performance profile under power management. For laptops, do not place them onto cooling stands. Let memtest run for 24 hours. If no errors, you dont have issues with the ram. – user986363 Jan 9 at 14:50

Testing can not prove the absence of bugs, only their presence

Memtest is great for finding errors in RAM. The rate at which is find errors is by necessity inversely proportional to how broken the RAM is. The more broken it is the faster it finds errors.

90% of the time, if the RAM has a problem, memtest will find it within 10 seconds, 99% of the time, one pass will be enough to find the issue. The longer it takes to find the issue, the more subtle it is and the less likely it is the cause a problem with your PC (but you should still get new ram if you get even one error)

As the your computer is crashing quite frequently and you have run a few passes, It's probably not your RAM. As a next step, you should test you hard drive and then CPU with a tool such as Ultimate Boot CD or Hiren's. (Most modern BIOS's also have a built in HDD testing feature)

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I suggest to try to clean the RAMs and socket and test them again first (use isopropyl alcohol; made positive experience with disinfection spray as replacement; But don't spray the latter one directly onto RAM - only onto the cloth as it shall only serve as resolvant and will eventually leave some residues when used in too high amounts) – Stefan K. Dec 8 '14 at 14:33

At work we usually left the machines running over night, but in all fairness, every time I've been able to show a memory problem with memtest it has been within seconds of starting it.

I've never seen a machine do 1 full pass to fail on one the following. (Not that it is necessarily impossible, just to show that it is rare.)

I used to work in a computer shop where we started memtest on new machines on a more or less daily basis.

Without enough info to really say so I'd still guess your problem is likelier an over heating or bad driver one.

Since you've tried more than one OS the driver part seems unlikely. Unless you've for example only tried different windows versions that use the same driver.

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I actually saw errors starting at pass 3. I assume this has to do with the warming up of the RAM, CPU and/or memory controller. All my problems of this kind were related to either improper connection of the RAM to the socket, socket to motherboard or debris on the RAM (as I took the RAM out, cleaned RAM + Socket connector and put the RAM back in which eventually resolved the problem). – Stefan K. Dec 8 '14 at 14:22
PS: I suggest at least 3 passes. While overnight with ~ 5-8 passes is more reliable. – Stefan K. Dec 8 '14 at 14:23
I've seen errors surface on a third pass, I believe due to heat. – benallansmith Mar 9 '15 at 3:07

100% coverage represents one full pass of testing your memory. In general it is better to run multiple passes. Here are three typical lengths of testing you might use:

  1. Test until 100% coverage (a quick test to make sure your RAM is functioning reasonably)
  2. Test for 1 hour (this will catch everything except intermittent of errors)
  3. Test overnight (recommended; your computer is not doing anything else at night anyway, why not be absolutely sure your RAM is good?)
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I have seen RAM pass the first 6 passes of memtest and then fail subsequent passes, and when running a Linux OS with that RAM would see locking up after a 6-8 hours. Other RAM on the same motherboard ran fine, so apparently the failing RAM was temperature sensitive.

When I suspect a RAM problem (e.g. Dell computers with diagnostic lights) I run memtest on one RAM module at a time in the first slot for 8-16hrs. If it passes that confirms both that slot and RAM module are good and I can (more) confidently use that slot to test other RAM modules.

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My experience with memtest86+ differs a bit from most people here. memtest86 has helped me a lot along the years but unfortunately it sometimes fails to detect errors.

Although memtest works the majority of the time, it failed me a couple of times. The first time it failed to detect errors i had a PC with 1x 4GB DDR3 that was giving me BSODs related to the memory. I ran memtest for an entire day, we're talking about 15+ passes but no errors. I then tested it on a completely different computer, same thing, no errors. Operating system was completely unstable but no errors on memtest. I then used a different software named "PC-Check" from Eurosoft which is very similar to memtest but uses different algorithms. It is also bootable, does not need any operating system. It detected errors in less than 5 minutes. I then was able to send the module to Corsair RMA and get a replacement.

So, memtest is very good but not always enough. I currently use memtest and PC-check to check memory. If memtest fails to detect errors, PC check certainly will and vice versa. And trust me, it happens more often than one would think.

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Given that, after one pass, it displays Pass complete, no errors, press Esc to exit, I always assumed that's sufficient.

enter image description here

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Err, if that is really the case, wouldn't memtest automatically stop after one pass instead of allowing us to carry on testing forever? – Question Overflow Feb 14 '13 at 2:54
@QuestionOverflow: I don't know, would it? – Oliver Salzburg Feb 14 '13 at 12:02

I do one pass to see if there are any obvious errors.

If there is an error no more passes needed.

If the problem with the computer is strange i let it go overnight or over day for ~10 hours just to be sure.

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I usually run memtest EVERY TIME I change CPU, memory or notice odd issues. Reason is - memtest does not just test memory. It will error out in three other important cases:

1) If there are issues due to overheating of either CPU or memory. Normally, memtest loads CPU for several of the tests to almost 100%.

2) if CPU cannot access memory correctly. Most of the tests read & write at all locations of the memory.

3) if there are problems with power. I.e. a weak power supply or bad capacitors cause too many spikes offsetting random bits.

If I see at least a single red error, I start looking for what should be removed / fixed before using the hardware.

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While this may be useful information, it doesn't answer the original question. – blm Jan 12 at 4:17

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