I'd love to spend some time discussing the technical details of how Advanced Clock Calibration works - Except we don't actually know. How ACC does what it does is a well-kept secret at the moment, but the general consensus is that this functionality uses six previously unused pins on the southbridge to perform some kind of additional tweaking to the CPU. These changes allow for some supposedly significant improvements (AMD quotes in the region of an extra 200MHz) to the overclocking potential of Phenom CPUs, making the use of an SB750-equipped system with a Phenom Black Edition processor a particularly exciting prospect - Needless to say we'll be taking a look at how ACC affects overclocking with just such a configuration during the course of today's review.