Spontaneous reboots on Intel i5 and FreeBSD 9.0

[Warren Block]

On Fri, 18 Jan 2013, kpneal at pobox.com wrote:

> On Fri, Jan 18, 2013 at 09:48:05AM -0700, Ian Lepore wrote:
>> I tend to agree, a machine that starts rebooting spontaneously when
>> nothing significant changed and it used to be stable is usually a sign
>> of a failing power supply or memory.
>
> Agreed.
>
>> But I disagree about memtest86.  It's probably not completely without
>> value, but to me its value is only negative:  if it tells you memory is
>> bad, it is.  If it tells you it's good, you know nothing.  Over the
>> years I've had 5 dimms fail.  memtest86 found the error in one of them,
>> but said all the others were fine in continuous 48-hour tests.  I even
>> tried running the tests on multiple systems.
>>
>> The thing that always reliably finds bad memory for me
>> is /usr/ports/math/mprime run in test/benchmark mode.  It often takes 24
>> or more hours of runtime, but it will find your bad memory.
>
> I've had "good" luck with gcc showing bad memory. If compiling a new kernel
> produces seg faults then I know I have a hardware problem. I've seen
> compilers at work failing due to bad memory as well.
>
> Some problems only happen with particular access patterns.  So if a compiler
> works fine then, like memtest86, it doesn't say anything about the health
> of the hardware.

Most test tools are like that.  They might diagnose something as bad, 
but they often can't prove it is good.  SMART has a reputation for not 
finding any problems on disks that are failing, and capacitors that 
aren't swollen or leaking still may not be working.

But diagnostic tools can at least give a hint.  In my case, memtest 
indicated a problem--a big problem.  I removed one DIMM at random (there 
were only two) and the problems and memtest errors both went away. 
Replace the DIMM, and both came back.