Just picked up a "Costa Rica" 3770K and so far at 4.8Ghz on air its only pegging 78C with intel burn test. It seems the first batch of Malasian ivy bridge chips were just terrible and the new batch's are far superior. My first chip was an 8th week chip and this new chip is a 19th week. Needless to say if you were to buy one today it would overclock a lot better then release chips.
That is a possibility but from reading over at various boards the newer the batch the better the temps and overclocking.
That happened with Sandy chips too, lol. The Costa Rica chips were supposedly the "good" ones (which I have a Costa Rica 2500K, actually). I never have put much stock into that though. I have a feeling that sentiment is just carrying over to Ivy now, with no real basis behind it. You just got lucky...
I had a Malay i5 3570k and the temps were not consistent running 4.6 at 1.35v never got past 75 celcius though with good watercooling . I purchased that chip in june 2012 , i broke it on the weekend , bought a new one and it's from costa rica , running the same oc it is 10 degrees cooler at load and the cores are more consistent