First up, from its Republic of Gamers series, we have the ASUS Crosshair IV Formula, which packs the high-end 890FX chipset with ASUS' own in-house features, some of which are pretty extreme. While we have seen ASUS' proprietary features in the past, there's one significant addition that's meant to complement AMD's Turbo Core technology. As you may know, what Turbo Core does is to basically increase the clock frequencies of active cores by a fixed amount when there are idle cores (three or more on a 6-core Phenom II X6). This feature is expected to make its way to future quad-core 'Thuban' based AMD processors, but ASUS has something special for its users.
Known as Turbo Unlocker, this feature works on Phenom II X6 processors and all other 'Black Edition' AMD processors and according to ASUS, will improve the performance beyond that from AMD's Turbo Core. In our tests, we found that to be true, though the amount of improvement could be quite minor. Turbo Unlocker will increase the CPU multiplier even further - on a Phenom II X4 955, we saw the default 16x go up to 16.5x when this feature is enabled (you'll need to install a small desktop application before using it). On a Phenom II X6 1090T, the increase was slightly more, going up to 3.8GHz for singly threaded apps (compared to 3.6GHz without) and 3.3GHz for multi-threaded workloads, (compared to 3.2GHz without).
No doubt, it's a small gain of at best, 3% in our benchmarks, but since you have already paid for it and there's little penalty at such small increments, we say keep it enabled. This small multiplier increase also explains why it needs an unlocked 'Black Edition' to work, since this feature directly tweaks the multiplier.
There's no doubt that the Crosshair IV Formula is targeted at the niche enthusiasts users, with many of its features too extreme for the average user. Of course, if you're considering an AMD 890FX, then you possibly fall within this group. The board itself oozes style with its red and black theme, a plus point for some users, while ASUS has naturally gone with the expensive components. Finally, layout was excellent and we could really find no fault here. The only sticking point is that 3-way CrossFireX is about as good as you can get here, and not the quad version that some may be expecting from such a high-end board.