# memtest fixed bad RAM?!

## Cyker

Summary: Bad RAM suddenly 'healed' after long memtest; Explanations?!

Okay, so a friend was complaining their laptop kept crashing; They'd be doing something then weird lines would appear on the screen, then crash.

Classic bad RAM symptoms on systems that use integrated graphics.

So to be sure, ran memtest and small-violin! Indeed there were many errors.

I think I had a phone call or something then as for some reason I went away and forgot about it.

2 days later I remember to check it - It's been running for near enough 2 days at this point and despite racking up 90,000 errors and many fails, I noticed with interest that it had 7 passes. WTF?

So I power-cycle the machine and run memtest again - No errors!!!

Waaaaaaaat?!

Has this happened to anyone before? I had already done the usual stuff of cleaning the contacts with switch cleaner, reseating the modules etc.

The only thing that currently springs to mind is if there were some tin whiskers or something on the BGA that were creating a teeny tiny short which have been fried by the RAM being hammered for 2 days straight.

I am now not sure whether to bother replacing the RAM or not...!

I've left it off to cool down for a while now just to see if it starts failing again, but this is pretty weird; Never seen this happen before!

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## frostschutz

 *Cyker wrote:*   

> Summary: Bad RAM suddenly 'healed' after long memtest; Explanations?!

 

Maybe it was infested with nargles?

 *Quote:*   

> I had already done the usual stuff of cleaning the contacts with switch cleaner, reseating the modules etc.

 

Maybe some cleaner residue left which evaporated thanks to the RAM modules heating up?  :Very Happy: 

I would not trust it and keep a very close watch on it. Memory errors are strange. I had memtest sometimes run for days without error, but after a reboot memtest showing errors immediately. The RAM was without question bad and booting into Linux would cause a system freeze within 24 hours regardless.

As long as the error is in a very specific region you can work around it and use the module losing a few KB/MB of RAM depending on the size of damage. If it's random or large-area you have no choice but to get a new memory module and hope it wasn't the mainboard / cpu

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## Syl20

 *Cyker wrote:*   

> Summary: Bad RAM suddenly 'healed' after long memtest; Explanations?!

 

Maybe a power weakness ? The 1 or 0 states of each memory area are just a voltage difference, after all. If the battery or the AC adapter don't give enough energy to the motherboard, that might cause such errors.

Was the battery charged when you got the laptop ?

However, getting new memory modules is encouraged. Just in case...  :Wink: 

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## Cyker

Yeah, at this point it'll be up to my friend to decide whether they want to pay for the new sodimms...

Would have been easier if it stayed broken so I could show them, but now I have no proof!!!

The switch cleaner shouldn't have left any residue (I learned the hard way that carb cleaner is NOT a substitute for electrical switch/contact cleaner when cleaning a car MAF sensor for this reason!)

Hadn't considered the weak power supply angle... the battery in this laptop appears to be dead so it could be sapping the volts down I suppose...

Personally I think it's the nargles... >_>

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## krinn

heat also, overheating ram appears dead ; when colder (not into the critical heat condition), the ram appears fine.

and when you say laptop, you should just always think about it as a "computer with heat trouble", because it's nearly always the case.

and many times, the line between too hot and "hot but still ok" for laptop can be cross by raising it a few allowing it to get fresh flow from bellow (and you may think "but i didn't change anything", when changing its position may be enough).

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## Goverp

I wonder if there were dirty connexions - my first action on electronic problems is to reseat all the connectors and chips, to scrape them clean of oxide, cruft and chocolate.

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## NeddySeagoon

Cyker,

Something drying out due to two days of running?

Electrolytic capacitors reforming/healing due to being left powered up?

Mechanical stresses causing issues that are only present during thermal transisitions?

Remove the DIMMS, wipe the contacts with an ink eraser (its mildly abrasive) put them back.

Let everything cool down and run memtest again.

When memtest finds errors, it indicates an issue with memory accesses.  It does not mean that the RAM is faulty.

If the errors occur at the same address and in the same test every pass, RAM is the likely problem.

Random errors indicate the issue is elsewhere.

As the machine has graphics in shared memory, you can determine if the issue is reads, writes or refreshes. I'm not sure that it helps.

Have a static display image.  If the image is generally correct but pixels or lines twinkle, you are seeing read errors.

The memory content for the image is correct but its being misread from time to time.

If the image decays over time, the RAM is forgetting .. that's a refresh issue.

If its written incorrectly the screen display will always be incorrect, but you probably not get booted to see it.

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## Cyker

Wow, thanks for all the replies!

The RAM hasn't missed a beat since it mysteriously healed itself; Tried it from cold, tried it hot, tried it leaned up at various angles, but we're replacing it anyway and also going from 6GB to 8GB so it's all good  :Smile: 

Lots of plausible theories here on the cause, although alas we'll never know what caused it for sure! 

I don't think it was dirty connections as I cleaned them and anyway, dirty connections don't usually get better on their own, which is what was so perplexing about this!

Hadn't considered the liquid one, but that would fit the symptoms if the heat from the memtesting evaporated it!

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## Ant P.

All computers try to pretend they're these abstract, neat digital circuits, but in the end they're really analog electronics with tons of state, crosstalk, reality and other nasty things happening all the time. So with that in mind, there's no point overthinking things like this.

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