AMD has recently cooked up a little something they like to call the Phenom II X4 TWKR Black Edition, a hand-picked, limited edition processor that is designed to be overclocked “to the extreme.” Currently labeled “Not for Sale,” with no serial numbers and only one hundred of these bad boys in existence, just a few lucky folks have got their hands on one, so we’ve dug up some reviews (and previews) so you can see what the fuss is all about. According to the company, one of these guys could be pushed by 100MHz with air cooling, which doubles to about 200MHz with “extreme cooling.” As far as impressions go, the reviewer at Neoseeker quickly decided that the units aren’t meant to be overclocked on air only, and that dry ice isn’t much better. Hot Hardware says pretty much the same thing. Though they weren’t able to test with liquid nitrogen or liquid helium (the only way to get real speed) they did put a Koolance LN2 pot (and about 20lbs of dry ice) to the test for 4.73GHz. For best results, according to Tom’s Hardware Guide, bench the the processor at -190