tetsuya23 :
I have no idea really either this is a good OCing batch of CPU's or I am just lucky that I got a good one from this "X" batch cannot determine unless someone in UK also have bought the same advertise chip from Scan and maybe we can compare results.
I too have got a X batch 4790k that overclocks good. I'm running it 24/7 with 47x @ 1.225v and 45x cache @ 1.15v.
My max stable is 49x @ 1.3v. So after delidding that thing I'm pretty sure it can make 50. I'm on water but not from the UK^^.
That's also a nice chip you got there!
Batch Number: X439B311