It'll bench at 4.6ghz if I want it to. However, after about four hours of Crysis 3 it crashed, so I wound it back to 4.5. Takes 1.29v.. The main issue is I am only using a 120mm single thick AIO, but saying that temps were fine (mid 60s).
Now I don't bother tbh. I hardly even use this rig because it's noisy (two 120mm AIOs in push pull) I mainly use my Fury X and Xeon rig because it's full water and very quiet (600 RPM fans). I have been using it lately for VR (the Titan XM rig) because obs it has more balls, but it hasn't struggled so I've just left the CPU stock.
It is luck though, though partly it comes down to when you bought your 5820k. IIRC I waited about six months into the release before retiring my 3970x. I really didn't want to, but my board went, MSI could not replace it and so I bought a new system with a warranty.
Later 5820ks were *much* better than the early ones, which could barely scrape 4ghz without hitting the 90s.