On 28/01/2015 01:28, walt wrote: > Yesterday I installed 4GB more of RAM in this machine for a total of 8GB, and > the machine soon began random segfaulting and even a kernel crash or two, so > obviously I suspected the new RAM was faulty. > > I let memtest86+ run overnight and it found zero memory errors. Today I > exchanged the new RAM anyway and got a different brand this time, and > that fixed the problem. > > My question is why didn't memtest86+ find any errors? Could it be that the > first RAM I bought was actually okay but this machine didn't like it for some > reason? Both were DDR3/1333MHz, just from different manufacturers.
RAM, like everything else made in a factory, is built to tolerances. So is your CPU and motherboard. A positive result from memtest+ (something failed) is definitive - there really is a problem and it is likely the RAM. Or maybe your RAM just doesn't like your motherboard but this is rare. A negative result from memtest (nothing failed) is not definitive - it doesn't mean the RAM and your system is not faulty, it just means memtest+ didn't find anything. Sometimes you have to run memtest+ for 48 hours to trip over the problem whereas your running OS does it immediately (it's a computer, go figure) Keep in mind memtest+ is an artifical testbed - it tries it's best to find issues but it's not the same thing as your running system. And there's lots of variables: Have you overclocked? Over or under volted? Is your PSU OK, could the running system stress it out? Or maybe timing tolerances between that RAM stick your motherboard are close to the edge. I think your machine just didn;t like that RAM and it would work fine in 999 other machines. It happens sometimes, manufacturing and test rigs are not 100 perfect. They are close, but never 100% -- Alan McKinnon alan.mckin...@gmail.com
