Thanx for the tip, I finally disabled it.

After numerous tries to achieve 8*400, I never got it stable at max vcore 1,1265v.
Not wanting to go higher on voltage, I gave the exact given in this topic configuration for the cpu, but running 4:5 833 MHz the memory @4-4-4-8 2.1v. (I'm still to stop thinking like that about the 6400 sticks)
I get an error in prime25 in about 2hours n 20 minutes.

I just did the vdroop mod and am running a smallfft's test with prime, waiting for the results. If I get an error again I'll loosen memory timings and ratio before giving any more voltage.
I'll post again when I finally get a stable system.

As far as you know, could it be the memory that's causing the errors? I mean since I'm running the smallfft's test that doesn't test memory as prime25 says.