Unless you have your case opened up with a high CFM fan blowing right on your card, or you're water/oilcooled, I call BS on your 70*C full load @ 1010Mhz....
I have 5 5830s running in my basement, with no additional "high CFM fans" blowing on them. All are running at 69-70C @ 1010/250 stock voltage. No cases. all open.
Ambient in the basement is about 20C.