Max 4890 OC
The early ones dont oc to good power regular parts get to hot.
Both of my cards run at 1.35 1.2v.
My early MSI @971 1071 needed a voltage increse to run stable.
MY 2nd 4890 is a HIS turo+ but is a decap version.
Decaps and circuit changes = a higher oc and a cooler running card.
The HIS gpu is 12c cooler on the Gpu.
The HIS will run at 1040 and 1100.
Do to CF both cards are set @971 1071.
Raising the volts gets the power regulating circuits temps to high.