Thanks for the procedure. I'll try the steps you recommend. I thought the default was 2000MHz 1,65V 8-8-8-24 2T... when you talk about default you are talking about the SPD values? I mean if I want to put frequency @ 1600MHz, I have to check if there is some SPD values for 800 and check the related timings ? Example with my memory: 1333MHz in the SPD tab of CPU Z shows 9-9-9-24 timing. But nothing with 1600MHz. I don't understand how is it possible to have worster timing @ lower frequency...but it is maybe because of the voltage @ 1,5?

I'll try this: 1600 7-7-7-20 @1,65V, then reduce voltage. Do you recommend to use mem test for checking if the setting is correct ? Or may I use Super Pi or Prime 95 to validate? It will probably take a while... but I'll try that way.
Some other questions:

- What is the benefit to reduce the tRAS?
- 1T and 2T what does it mean?
- tRC and tRFC is that the same thing? Because in the XMP profile the value is 51 but it's not stable if I manually put tRFC @ 51 into the bios (in auto mode, value is 98...).

There is maybe a tutorial explaining that, sorry for beginner's questions.