Debugging bad memory problems

Sun Apr 26 21:05:52 UTC 2015

On Sun, Apr 26, 2015 at 10:05 PM, Valeri Galtsev
<galtsev at kicp.uchicago.edu> wrote:
>
> On Sun, April 26, 2015 12:11 pm, Fernando Apesteguía wrote:
>> Hi,
>>
>> I suspect my old and beloved AMD64 laptop is suffering from bad memory
>> problems: I get random crashes of well tested programs like sh, which,
>> etc even when I executed some of them from /rescue.
>
> If RAM is a suspect the first thing I would do is re-seat memory modules.
> Open the box. (Observe static precautions!) Remove memory modules. Install
> them again.
>
> Do memtest86 (by booting into memtest86, you can have that in your boot
> options, or you can boot off external media as others suggested).
>
> If you still have problems: try to run with one memory module instead of
> two. At some point when they went to higher RAM speeds memory bus
> amplifier became more fragile (some chips, some manufacturers, as not it
> is part of CPU, this may be true only about some of the CPU models). You
> sometimes can slightly fry it if you merely leave laptop running on
> battery, letting battery run down and laptop powering off due to that.
> With some of chips this may lead to slightly frying it - memory controller
> portion of it, address bus amplifier in particular. Bus amplifier becomes
> slightly lower frequency, which results in poorer handling capacitive load
> (which is larger if you have more RAM), and it is marginally OK,
> occasionally having address errors. Going to one module may resolve this.
> You will know if this is likely the case if memtest86 is successful with
> each of single RAM modules, but fails (in random places, often not
> reproducible) with both.
>
> Good luck!

I booted from a memtest CD-ROM. It passed a couple of tests fine and
then it rebooted while doing a "bit fade" test at around 93%. Removing
the modules is tricky since this laptop has screws all around in dark
corners (even removing the battery needs a screw driver). I will try
to limit physical memory with hw.physmem and see if it makes any
difference.

Thanks!

>
> Valeri
>
>>
>> I wanted to check the memory banks. I installed
>> /usr/ports/sysutils/memtest86+ and try to run it at boot. According to
>> the documentation, from the boot loader prompt:
>>
>> unload
>> load /boot/opt/memtest86+
>> boot
>>
>> But at the time of loading the file, the laptop reboots.
>>
>> I also tried /usr/ports/sysutils/memtest. But when I run it (as root), I
>> get:
>>
>> $memtester 1G
>>
>> memtester version 4.3.0 (64-bit)
>> Copyright (C) 2001-2012 Charles Cazabon.
>> Licensed under the GNU General Public License version 2 (only).
>>
>> pagesize is 4096
>> pagesizemask is 0xfffffffffffff000
>> want 1024MB (1073741824 bytes)
>> got  1024MB (1073741824 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073737728 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073733632 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073729536 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073725440 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073721344 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073717248 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073713152 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073709056 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073704960 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073700864 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073696768 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073692672 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073688576 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073684480 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073680384 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073676288 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073672192 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073668096 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073664000 bytes), trying mlock ...too many pages,
>> reducing...
>> got  1023MB (1073659904 bytes), trying mlock ...too many pages,
>> reducing...
>>
>> ...
>> ...
>>
>> got  0MB (73728 bytes), trying mlock ...too many pages, reducing...
>> got  0MB (69632 bytes), trying mlock ...too many pages, reducing...
>> got  0MB (65536 bytes), trying mlock ...locked.
>>
>> Any help with these two problems or any alternative programs?
>>
>> Thanks in advance.
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>
>
> ++++++++++++++++++++++++++++++++++++++++
> Valeri Galtsev
> Sr System Administrator
> Department of Astronomy and Astrophysics
> Kavli Institute for Cosmological Physics
> University of Chicago
> Phone: 773-702-4247
> ++++++++++++++++++++++++++++++++++++++++