Different voltages ddr3 rams

If you use 1.7V, try setting the RAM to 1333MHz, then boot into memtest86+ (from the .iso file), to see if your RAM passes the tests - they take about 45 mins to run (unless there are errors). If that doesn't work, take them back down to 1099MHz and run memtest again.

Firstly, i booted f8 bios then I tested each rams with memtest86 v4.00 and both passed @1600mhz and 1.7v (4 times). However, when i used them together there were some errors @ 1600mhz or 1333mhz, from 1.7v to 1.9v. I can use the first ram(1.7v or 1.9v, 1600mhz) perfectly if i use only it . And interestingly, when i used only the second ram (@1333mhz or 1600mhz) win7 or ubuntu 10.04 could not be booted even the ram passed the test. There is something wrong and i don't know what it is. So any suggestions?

I tried using only 2nd kit too. It passed memtest86 several times without error but it crashes sometimes, while booting windows or anytime freezes forever. I think the problem is with this ram because the first ram is very similar and there is no problem with it. However, the 2nd ram passes memtest86 so i'm not sure about giving it to guarantee service.

Thanks for the advice. I'll give and wait for new one.

also the first ram works without error @1.7v 1600mhz and passes memtest86 but @1.66v or 1.64v it gives some errors so does it mean that if they give me a ram working @ less than 1.7v the rams can't work together @ 1600mhz