What's a safe voltage I can run a i5 4670k on, to keep it

Try from 1.20 to 1.25, mine around 4.1ghz worked even under 1.2v. You can go over that anyway but you need a really good cooling system when you approach 1.3v

>>55979634
Fuck, the mobo i bought ( a used z87) came with 1.9v IIRC.
I really have to take a look into those.
I'm using a cooler master 212x, it's keeping somewhere around 45° on 4Ghz while gaming.

>>55980584
Intel says it can work fine at 70 C, I'd stay about 60 to 65 as maximum to be safe. Mine is pretty shit I can get in to 4.3 Ghz no problem but if I want to put it to 4.4 I've to go over 1.3v. On average you should get 4.4 with reasonable voltages. Anyway while you test for stability put the voltage fixed because there are some stress test that overvolt when the processor use type of instructions, when you are sure that you're stable switch to adaptive voltage to save power

>>55978850
Would be cool to live in a Japanese town like that.