It will be hard to go over 2.8GHz only adjusting the multiplier, especially with the stock cooling. To squeeze more out of it you should lower your HT link multiplier to 5x (1Ghz 5x200 MHz). A lower HT multiplier will help with stability and you can raise the HT link multiplier back up latter (incrementally and testing for stability at each step) after you have settled on a final CPU overclock. With a lower HT multiplier you can also lower the CPU NB voltage (the northbridge memory and HT link controller in the AMD CPU) one or two steps. That will help a little with temps. Even with all that some Kuma samples will not be able to reach 3.0GHz at stock voltage so you may just have to raise up the vcore a step. If you do, I hope you're using something better than the stock cooler, or at least have good case ventilation. 😀