GPU
325MHz - stock (1.77V?)
330MHz - 1.8V
345MHz - 1.9V
355MHz - 2.03V
360MHz - Black screen at any voltage
=> 357MHz at 2.05V; GPU ~ 35°C load
It seems that I'm hitting a wall at around 360MHz I can increase the voltage over 2.1V, but it doesn't help me get it more stable.
MEM
566MHz - stock (3.45V?)
600MHz - 3.55V
610MHz - 3.66V (with artifacts)
615MHz - 3.6V (heavy artifacts)
=> 620MHz at 3.6V; MEM ~ 50°C load
620MHz isn't always stable and I have heavy visual artifacts. The score still scales upwards, so ... I'm fine with it. Increasing the voltage up even further doesn't help, so I guess the only thing left to do is decrease the temperatures