HW canucks tried to overclock the 9590. http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/62166-amd-fx-9590-review-piledriver-5ghz-18.html
"Since our Corsair H80 and Noctua NH-U12S were both overwhelmed whenever Turbo Core was disabled and the system was left at idle (yes, you read that right: at IDLE), we decided to step things up a notch. Bringing in a Noctua NH-U14S with dual fans as a pinch hitter resulted in more acceptable temperatures and allowed for some overclocking. Though not all that much."
"With Turbo Core disabled and a bit more voltage, we were able to achieve a constant frequency of 5.016GHz on ALL cores, regardless of the situation. Unfortunately, we couldn’t get this 300MHz to a point that we would consider 24/7 stable due to the elevated temperatures it caused but it was more than capable of running a few benchmarks. "
"Throwing caution into the wind, we decided to push things even further and eventually hit nearly 5.2GHz. Unfortunately, while the system would boot into Windows, any multi-core load would shut the whole works down. No BSOD or OS freeze, just a complete reboot. It could be that at that point, we had reached the motherboard’s power limits but testing continues. "