Guys, did you read the new "FREE" issue of Overclocker Magazine#13? I've read it, and this is my "REPORT" for you!
They wrote about SB cpu overclocking at a higher clock simply by downloading a bios fix for your specific MOBO.
Some guys OC'd on air reaching 5.5GHz, "STABLE", I mean as stable like a 4.8GHz stable. While some of us manually OC reach a wall of 4.8GHz or 5.0GHz, the bios fix will release the full OC capability of your i7 2500k or 2600k cpu. They're talking about a bios option of enabling the "INTERNAL PLL OVERVOLTAGE".
I suggest you DL the MAG(pdf) from TH. The article is in the news section of TH, or go directly to http://www.theoverclocker.com/ to DL it! Issue #13.
This is a link of a forum where some peeps are already doing it.
theyre plenty of online stuff on overclocking, i wouldnt personally buy just a magazine dedicated to it, find it somewhat boring to read too much about this subject, the thing that makes a good pc magazine are technological advancement in tech, and also great how to do articles, and funny bits here and there, hardware uk is quite good and i read a magazine from france , as well to improve my french