Hi my pc:
4790k stock
corsair 750rm
ram:
http://www.morele.net/pam...8gx3m2a1600c9w-41?635/

Corsair Vengeance Low Profile 2x4GB 1600MHz, DDR3, CL(9-9-9-24), XMP White (CML8GX3M2A1600C9W)


I am using stock settings in bios. Auto settings. Also when i am testing memtest sometimes after 5 minutes i have errors. But sometimes after 24 hours i dont have any single error. Any suggestions? One time i run memtest then after 5 minutes i have 34 errors. Second time when i run memtest it can go even 24 hours without single error.


My system is stable , i run SuperPi 32mb no issues. Prime95 10 hours no errors. Also games are stable benchmarks itd.

Can you help me? Even that i must change ram?

Can somebody explain me this? This is weird, now i am in test 24 hour no single error. But yesterday i had 34 errors after 5 minutes.

It might help to know what motherboard you have, but I would carefully reseat the RAM and then go into the motherboard BIOS and manually set the RAM speed, timing and voltage to the Corsair tested specs or set the BIOS to use the RAM's X.M.P. profile..There should be information on how to do that in your motherboard manual..Using the auto settings in BIOS will result in the RAM running at it's lower/slower SPD specs, which should, but not always, work properly..If you still encounter errors, you should read the MemTest86 Technical Information about Troubleshooting Memory Errors..Since Vista (If I remember correctly) Windows has a built-in Windows Memory Diagnostic tool too, just FYI.

+1 on Reseat the Mem Cards

+1 on Reseat the Mem Cards

I can run Prime 95 without errors, SupePi , games are stable. However yesterday memtest shows errors after 5 minutes of test. I repeated test and now i am in test 24 hours without errors. So errors dont back. 
Today i am running memtest 24 hour without any errors. So it can be still memory or memory controller in cpu?


If memory errors in memtest are random ( not in the same places in test ), can be issue with cpu memory controller?


Change ram or cpu then? Please help

Go to your motherboard (whatever it is) manufacturers website and get/install the latest BIOS update if needed..There may be updates that address memory compatibilty and/or other issues.

I have had similar issues with different board/memory before. I used Intel BurnTest and was able to narrow down the problem to the memory, so you should try that. It works pretty much all the time to confirm the issue. If you have spare memory, swap them out and try that too.