Date: Fri, 18 Jan 2013 13:23:00 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: kpneal@pobox.com Cc: freebsd-stable@FreeBSD.org, Ian Lepore <ian@FreeBSD.org>, Ronald Klop <ronald-freebsd8@klop.yi.org> Subject: Re: Spontaneous reboots on Intel i5 and FreeBSD 9.0 Message-ID: <alpine.BSF.2.00.1301181313560.1604@wonkity.com> In-Reply-To: <20130118173602.GA76438@neutralgood.org> References: <CAJ-UWtSANRMsOqwW9rJ6Eebta6=AiHeNO6fhPO0mhYhZiMmn4A@mail.gmail.com> <op.wq3zxn038527sy@ronaldradial.versatec.local> <alpine.BSF.2.00.1301180758460.96418@wonkity.com> <1358527685.32417.237.camel@revolution.hippie.lan> <20130118173602.GA76438@neutralgood.org>
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On Fri, 18 Jan 2013, kpneal@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.
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