Date: Sat, 16 Jan 1999 09:27:01 +1100 From: Peter Jeremy <peter.jeremy@auss2.alcatel.com.au> To: freebsd-current@FreeBSD.ORG Subject: Re: Weird file corruption? Message-ID: <99Jan16.092624est.40330@border.alcanet.com.au>
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Zach Heilig <zach@uffdaonline.net> wrote: >Except simm checkers don't always catch errors, so if the simm passes, >there still is no guarantee (but simm checkers do weed out obvious >duds quicker than trying in a system). Unfortunately, there is no >conclusive test [that I know about] to prove a simm is "good". I'd agree with that. The guts of a DRAM (or any type) is high-speed analog circuitry with delicate multi-phase clocking (the external clocks and selects are internally subdivided into maybe 20 phases). There can be pattern-sensitive crosstalk between rows or columns that depends on inter-access timings - or even how long since a particular row was refreshed. I suspect it's impossible to prove that a SIMM is good - there are two many combinations to test. >Even better is to only use motherboards that support parity and/or ECC, >with parity/ecc simms/dimms. This is the only practical way to detect memory problems. A subsidiary problem is that, unlike say Solaris, FreeBSD doesn't automatically report ECC errors. Without this, your memory controller can be furiously correcting a hard single-bit error and die when it glitches to a double-bit error. Someone did post a script that checked and cleared the relevant register in an i440 several months ago, but I seem to have mislaid both the script and reference :-(. Peter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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