Nice overclock!
What motherboard are you running and do you know have your chip info for like the date it was made, etc?
It was a retail box from the egg, box is at the shop.
All the D0 stepping i7s seems to really clock well with minimal voltage.
I am really not running any voltage on ICH/IOH cores either - just a bare minimum bump.
The QPI/VTT got the biggest increase but everything is still within OEM voltage spec!
The board is a Gigabyte Extreme X58 UD7 I have a MIPS fusion watercooling block on the way to replace the crap/restrictive stock unified north-bridge waterblock.
Id have to use a lighter memory base clock for the next big leap, right now its perfect. I am running my DDR3-1600 right at 1600 MHz @ 8x with tight timings at 4.2 GHz.
Any higher then this she really wants a 6x BCLK - which means id have to go the next big leap to bring RAM speed back up (IMO not worth the stability decrease or heat increase).
I poked her up into the 4.3-4.4 area briefly but it wasn't stable with that 8x Mem BCLK, with some tweaking im sure shed run 4.4-4.5 no problems; just really isnt a point.
Maybe when cheaper faster DDR3 comes out I will push for higher numbers.
Right now the ratios are perfect, cool, and stable so I think ive found my home for the time being.
I am happy at a low volt 4.2 GHz daily driver.