Fr3ak
Nice guide, but I have a few questions about memtest. Some ppl say that 25 passes of test 5 is enough to say its stable. How about that? I even get about 14errors per pass with default test with 100x10, cpu at 1.7v, ram at 3.2v, single 512mb stick.... So it has to be errorfree for 24hours with default tests to be stable?
A good question
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About memtest86 test #5 specifically:
felinusz
Many people also use specific memtest86/memtest86+ tests by themselves, to test out a new FSB or memory overclock quickly in order to see if it’s likely to be stable or not. Tests 5 and 6 in particular are good for this. However, 24 hours of all the tests on loop is your end-all solution to memory stability testing.
I should add, that I personally test my memory with test #5 looped for 24 hours, in addition to using all of the default tests looped for 24 hours. Test #5 is a great tool.
About the 24 hour time period specifically:
felinusz
As with Prime95, 24 hours really is required for a complete and thorough memtest86/memtest86+ stability test, and for the exact same reasons. I’ll quote myself for reference sake.
From Above
When you are stability testing with Prime95, you want to run the Torture Test for at least 24 hours. Why 24 hours?
There is a very common misconception that if your machine can pass Prime95 stability testing for, say, four hours, your machine will be able to run stable, regardless of what you are doing, for four hours as well, without issue. This is simply not the case.
Prime95 often finds errors in its 16th - 20th hour of testing, a potential for instability that wasn’t found after only four hours of testing. After only four hours of Prime95, the potential for instability still exists. 24 hours of Prime95 is a slight ‘overkill’, but you can never be too careful. 24 hours is widely viewed as a sufficient time period to catch any instability that may be present, but by all means test longer if you are able.
Now, for fear of typing lots and lots (Which I know that am about to do!), let's take a look at stability in general - the concept, in order to answer this question properly.
When it comes to stability; something is either stable, or unstable. There is really no grey area, "between" stability and instability, your overclock/hardware is either stable, or it is unstable. Yet, it is common for us as overclockers to say things like:
"My overclock is 99% stable, it's almost there, I just need more voltage/testing"
"It is fairly stable at this speed"
"It is bench stable"
These are
technically incorrect things for us to say. All of the above are actually
unstable!
That said, the very nature of stability, means that there is always a
potential for instability lurking around the corner. Just because you stress test for 1000000 hours, does not mean that the hardware
cannot potentially crap out on you in the 1000001st hour of stress testing. There is no degree to hardware stability besides 100%, and 0%, yet also no true proof of 100% hardware stability, unfortunately.
This is why we need a standard, that has proven itself to be very thorough.
When we stress test our hardware, we want to be as thorough as we can. The "24 hour rule" is simply a standard, based on the experiences of myself, and many other overclockers. It is
possible to stress test something for 24 hours, and still have a potential for instability. But is it likely? No, not very likely at all.
So, having gone about this in a very roundabout way, I can say that 25 passes of memtest86 test #5 is
not very thorough, and is largely insufficient as a means of weeding out instability in your memory overclock.
If you want to test for longer then 24 hours non-stop, by all means do so - be as thorough as you can be. However, stress testing longer then 24 hours could be deemed redundant, and would not leave us much time for overclocking
!
My apologies for the rambling post
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