Quote Originally Posted by alcattle View Post
I might be mistaken but is the i7 8xx series the new chip form (1156?) and need same MB as the i5.
In addition to being a newer platform it has the new turbo modes. This is where it can "self-overclock" one core to a very high level if nothing is running on the other cores. This keeps the total heat level down to what it can deal with and gives a good boost to single-threaded apps.

That being said, it makes it a bad choice for a multi-boxing machine if you want to run at higher than stock speed because it is much harder to stably overclock this chip compared to ones that always run at the same level. You can disable the turbo on the i870 and get more stable overclocks, but then it's really just a wrong-socket i9x0 chip.

From:
http://www.anandtech.com/cpuchipsets...634&p=18&cp=33

For best performance with all four cores active, disabling turbo mode is the way to go. Otherwise you have to reduce the BCLK in order to make sure your system is still stable when the one-active-core turbo mode kicks in. For example, with our Core i7 870 with turbo disabled we hit 4.2GHz using a 200MHz BCLK. If we used the same BCLK but left turbo enabled, when only one core was active we'd hit 5.4GHz - clearly not realistic with only air cooling.