The X6 1090T is a Black Edition processor, so its multiplier is unlocked for easy overclocking. Combine that with Turbo Core and AMD's Windows-based Overdrive tweaking utility, and you have utter, total control over the way this thing operates. AMD exposes all of the knobs and dials for Turbo Core right in Overdrive, so you can define how many cores will Turbo up and how far they'll go.
The utility even lets the user choose the peak voltage used when cores range into Turbo territoryand yes, all of this overclocking goodness works seamlessly in conjunction with Cool'n'Quiet, for lower power draw at idle. As always, Overdrive offers control over the regular, non-Turbo clock multiplier and CPU voltage, too, so you can brew up your own cocktail of excess for both lightly and heavily multithreaded workloads.
Here's a look at the Overdrive monitoring page in action during one of our overclocking attempts. The cores' clock speeds range between 3.2GHz and 3.6GHz, and oddly enough, the CPU voltages appear to vary from one core to the next. (For what it's worth, I believe the Phenom II has a single voltage plane for all cores, and I'd chalk up the variance here to monitoring lag in a very dynamic situation.)
Faced with the prospect of getting to play with all of these knobs and dials, we took the rare step of forsaking our beloved BIOS-based overclocking methods. Via Overdrive, we created a custom profile for our Phenom II X6 1090T that had a base clock of 3.9GHz at 1.4V and a Turbo Core clock of 4.3GHz at 1.525V. I'm not sure what to make of this, but that config seemed to be optimal. Although we were using a beefy tower cooler that generally kept CPU temperatures in check, raising the base clock for all six cores to 4GHz just didn't work out well for us. One of our test apps would crash or the system would lock, despite raising the base CPU voltage as far as 1.525V. Similarly, taking the Turbo Core max to 4.4GHz wasn't stable, even if we pushed the Turbo voltage up to 1.55V. Perhaps with a little more tweaking, we could have hit 4.3GHz stable across all six cores, or a larger subset than the Turbo Core default of three, but we devoted an awful lot of time just getting as far as we did.
Here's how the X6 1090T performs at those considerable clock rates:
It's faster than a Core i7-975 Extreme, which is pretty darned good. Still, that's a fair distance from the monstrous Core i7-980X.
What about power consumption at this speed and voltage?
Since all of its power-saving mojo is intact and working properly, the overclocked 1090T draws no more power at idle than its stock-clocked self. Peak power draw is up considerably, well above the Core i7-975 Extreme, but not quite to the dizzying 322W zenith that the overclocked Core i7-980X system reaches. With good aftermarket cooling, you may find a decent amount of headroom of the Phenom II X6, as we did in our sample.