This was an article I posted on here a while back - http://www.bit-tech.net/news/hardwar...haswell-heat/1
I found this bit interesting -
"One manufacturer claims that pre-release chips marked as 3.5GHz parts were tested completely stably at 4.8GHz, but of the 40-50 retail units the company has tested not a single one has managed to reach above 4.2GHz without hitting unsafe temperatures or requiring too-high levels of voltage. Another firm has stated that it has had to drop plans to offer pre-overclocked Haswell systems running at 4.5GHz - a figure, again, planned based on engineering work carried out on pre-production samples provided by Intel - to 4.3GHz in order to ensure stability. 'There is a big difference in the overclocking potential between early Haswell samples and retail,' the unnamed manufacturer claimed."