How long to run memtest?

[ZeBaarda]

Hi, I read in different forums, that people do run it for a hour, some run more, some leave it overnight, some do 24hours and more! Some people (OC people say) say, that there is no need to go past 6-8hours, because 24h+ its a ram torture and memtest can find a error where it in reality doesnt exist, so i dont understand.. i usually do 24+! but dont know if its healthy? Some say, that even on a stable system if every component is in best shape, if u will run memtest for a week, or month sooner or later there will be a error, memtest will show one, so i dont understand how long is enough..
im really confused, but it could be true, that if u torture a stable ram at stock settings long enough, ram gets tired or hot and will show a error from overheating or else what, so.. waht do you think how long to run if temps are ok and ram is operating in normal conditions, stock manufacturers voltages and timings/other settings?
And are there types of errors, that could mean a serious danger and errors, that are not harmfull?

[David (PassMark)]

There is no fixed rule.

However here are some general comments.

• After a while (maybe 15min) the RAM won't get any hotter. It will reach a stable state, assuming the system fans are working.
• RAM isn't reliable. Which is the reason for ECC (self correcting RAM). There is a level of background errors that occur with all RAM due to things like cosmic rays. These are typically random events. You might get one after 5min, or might go a few months without one. So it doesn't hurt to repeat the tests sometimes. Too many random errors is likely a hardware fault, or a consistent error at the same address or same bits is likely a hardware fault.
• The more RAM you have the longer the test will take. More RAM = More testing time to get the same coverage.
• Slow CPUs & RAM will take longer
• Motherboards that can't multithread will take longer.
• There should be no concern that you are going to wear out your DRAM after 1 or 2 days of testing. DRAM doesn't wear out to any significant degree (unlike Flash memory).
• The changes of finding an error in the first couple of hours of testing are much higher than finding an error 12 or 24 hours into a test.
• If you are pressed for time, do a single pass of the test. If you have more time, do 2 to 4 passes. The probability of finding new errors after the 4th pass is pretty low.