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Lenovo T460s RAM problems

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Lenovo T460s RAM problems

Postby djrespect » Fri Apr 16, 2021 11:08 am

Hello everybody!

I'm having serious trouble with my 460s, which recently started freezing. If it does there are some strange lines and squared on the display and it stays like that until I do a reset. But I also got bluescreens twice which said:
- KMODEEXCEPTION NOT HANDLED
- IRQL NOT LESS OR EQUAL

Talking to a guy from Lenovo support he said that this is probably RAM related, so I removed the RAM (there are another 8GB soldered to the mainboard which are fixed) and the problem dissapeared. So I ordered new RAM but the problem appeared again!
So the problem is definitely RAM related, but the RAM itself doesn't seem to be the problem.

Any idea what else I could try?

(I also talked to a local repair tech and he said the only thing they can do is change the mainboard, which of course is not an option...)
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Re: Lenovo T460s RAM problems

Postby CS70 » Fri Apr 16, 2021 1:15 pm

The problem is that one of the device driver software that the OS uses to talk with the hardware is failing. That can be due to to an issue with the driver software, or can be an issue with the hardware, or a combination.

IRQ etc is a segmentation fault - a kernel level process is trying to write in a memory space where it shouldn't (the hardware tells it it shouldn't).

KMO etc means that a Kernel mode exception has occurred.

If a driver does something wrong, it may end up messing up a memory address, where then it goes looking. Since the messup is random, the address may end up either in its own memory segment, or outside. If it ends outside, the IRQ exception will be raised immediately since it's not allowed to. But if it ends up in its own segment, it will read a random value... and when it's going to try to use it, a kernel exception will occur because the value is not what the software expects (there's also the more subtle possibility that the value is simply wrong as opposite to unacceptable, which would result in odd unexplicable failrues).

Of course if the RAM or the access buss is broken it could be that the value that is read is not the value that was written, but your PC should fail more consistently.

There are various things you can do:

- when the blue screen occurs, it usually tells you the name of the software that has failed (something ebdubg with .sys or .dll usually).. take note of it and, if its always the same, it's a strong indication of which driver is bad
- check the event viewer for unexpected crashes, which can give you the same data
- start windows in safe mode with networking or even command line and see if the failures occur. They still might - if a driver for say the chipset has gone wrong it will still be operating in safe mode, but if they don't, it's an indication that it's the driver for one of the non-essential peripherals that is giving you trouble.
- use low-level diagnostics utilities in the BIOS to check RAM, buses, graphics ram etc

If the issue is hardware-related, the problem will occur even with the smallest possible operating system - the command line recovery interface. But hopefully not.

Another possibility is that it's the graphics card RAM or the driver that is broken - the fact that lines appear on the screen seems a hint. The specific of the PC will tell you if there's anything you can do to test (like disabling the built-in card).

If you manage to identify the troublesome driver, you can remove or reinstall it.
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Re: Lenovo T460s RAM problems

Postby djrespect » Sun Apr 18, 2021 10:27 am

Wow, thank you very much for your detailed answer! :clap:

I already did a memory test with Lenovos UEFI diagnostics and it also crashed while testing. And the problem does appear consistently after a one or two minutes after startup. So it really seems as if it is a hardware error, but like I said I'm pretty sure the RAM itself is not the problem so it has to be the connector or something similar....

The bluescreen hasn't appeared anymore, it just freezes and displays weird stuff (I'll try to post a picture later).

Edit:
I just installed it again to do some more tests and it immediately crashed while startup. I installed a different RAM and entered BIOS, but after a minute it also crashed. If I then push on the body of the laptop the display changes!

Image

Image
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Re: Lenovo T460s RAM problems

Postby CS70 » Sun Apr 18, 2021 5:21 pm

With hardware issues, all bets are off unfortunately :(

You're right that it may not be the DRAM bricks.. it can be anything that has to do with operation.

If this happens within a minute or so, it could be temperature related. I once had a problem with a pc which was freezing, and it turned to be that I had not applied the thermal paste on the CPU well enough, so the CPU was overheating. Removing the coolant and re-applying the paste fixed everything, and that pc has worked flawlessly for years after.

Your motherboard has most likely an integrated GPU, it could also be the culprit...

But of course it could be anything :(
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Re: Lenovo T460s RAM problems

Postby shufflebeat » Sun Apr 18, 2021 8:59 pm

Definitely not an authority on this subject, but...

I've been keeping an eye on this and am reminded of a lot of talk around this model concerning overheating, particularly the "s" variant. This would seem to tie in with CS70's suggestion.
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Re: Lenovo T460s RAM problems

Postby djrespect » Sun Apr 18, 2021 9:20 pm

Thanks again for your help, guys!

As I wrote in my first post, the laptop runs absolutely fine when I remove the additional RAM and just use the 8GB that are soldered permanently to the mainboard!
So it definitely has to do with the RAM slot, but since the problem is the same with two different RAM bricks, it's unlikely that it's the RAM itself.
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Re: Lenovo T460s RAM problems

Postby shufflebeat » Sun Apr 18, 2021 11:29 pm

djrespect wrote:So it definitely has to do with the RAM slot,

Or, logic would suggest, something up/downstream of it (not sure which way metaphorical "streams" flow in this context), implying it could still be something not directly related to the mechanics of the slot itself.

I'll back away now because I'm quite a long way out of my comfort zone.

:)
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Re: Lenovo T460s RAM problems

Postby CS70 » Mon Apr 19, 2021 8:33 am

djrespect wrote:Thanks again for your help, guys!

As I wrote in my first post, the laptop runs absolutely fine when I remove the additional RAM and just use the 8GB that are soldered permanently to the mainboard!
So it definitely has to do with the RAM slot, but since the problem is the same with two different RAM bricks, it's unlikely that it's the RAM itself.

Ah, sorry, hadn't caught on that. RAM type and timing? Are the bricks you're using in the list of brick types certified for that laptop? If it is, something seems indeed to be broken. If it isn't, that's likely your problem.
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Re: Lenovo T460s RAM problems

Postby djrespect » Mon Apr 19, 2021 9:07 am

CS70 wrote:
djrespect wrote:Thanks again for your help, guys!

As I wrote in my first post, the laptop runs absolutely fine when I remove the additional RAM and just use the 8GB that are soldered permanently to the mainboard!
So it definitely has to do with the RAM slot, but since the problem is the same with two different RAM bricks, it's unlikely that it's the RAM itself.

Ah, sorry, hadn't caught on that. RAM type and timing? Are the bricks you're using in the list of brick types certified for that laptop? If it is, something seems indeed to be broken. If it isn't, that's likely your problem.

One of them came installed with the laptop when I bought it and worked fine the last five years. Since I suspected this to be the problem, I bought one from Ebay which is on the list of compatible parts from Lenovo.
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Re: Lenovo T460s RAM problems

Postby CS70 » Mon Apr 19, 2021 9:31 am

Yeah, sounds like something's off. The fact that things change if you push the body suggests a physical issue - a socketed chip which has gone slightly off, a ribbon connector which has done the same, a dodgy soldering someplace. Old batteries are known to "grow" in size and push other components around which can crack boards when everything is packed tightly. Thermal expansion can do the same but if it now happens right on start with the computer cold, it's unlikely. Bad cabling can do the same. Perhaps simply opening it to change the bricks has exacerbated the problem.

Do you get the same if you connect and external monitor? Maybe something with the flat cable connecting the motherboard to the laptop screen. But the options are endless unfortunately. :(
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Re: Lenovo T460s RAM problems

Postby djrespect » Wed Apr 21, 2021 8:35 am

CS70 wrote:Yeah, sounds like something's off. The fact that things change if you push the body suggests a physical issue - a socketed chip which has gone slightly off, a ribbon connector which has done the same, a dodgy soldering someplace. Old batteries are known to "grow" in size and push other components around which can crack boards when everything is packed tightly. Thermal expansion can do the same but if it now happens right on start with the computer cold, it's unlikely. Bad cabling can do the same. Perhaps simply opening it to change the bricks has exacerbated the problem.

Do you get the same if you connect and external monitor? Maybe something with the flat cable connecting the motherboard to the laptop screen. But the options are endless unfortunately. :(

I checked the mainboard for any loose cables, ribbon connectors or any obvious visual faults but found nothing.
I'll try with an external monitor as you suggested, but other than that I think I will have to put up with the situation of having only 8GB RAM for now.

It's a really shitty situation: if the laptop would be completely dead I would of course be vexed but just get a new one. But since it's working perfectly fine without the memory expansion, it's hard to justify spending that much money.... :roll:
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Re: Lenovo T460s RAM problems

Postby CS70 » Wed Apr 21, 2021 8:52 am

Agree, so annoying.

The fact that you get occasional graphics fuzz with the additional RAM in is interesting: most built-in laptop graphic card allocate system RAM - and if at power cycle the allocated memory happens to be in the new bricks (and either them or the access circuitry to them is malfunctioning) it would lead to exactly what you are seeing.

I don't know enough of your laptop's firmware to say, but it is possible that it allocates different chunks of memory in different power cycles, in which case you would experience different failure modes - sometimes the graphics, sometime system crashes, sometimes nothing until the system is under load.

It all seems to point to the the bricks or the access circuit being bad.. or, is the BIOS up to date? Adding RAM may have mixed the access timings and if the BIOS is buggy that may lead to issues like you are seeing. Can u control the RAM timing manually?
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