new gigabytes are 1000mhz/1.25v , just install r43 bios and its back to 1.09V/900.
than set clocks :
1000/1250 - 610kh and waaaay cooler , less problems
or:
1100/1250 [1100/1500 on linux or bad drivers] - 650-660kh and still cooler than default
Install a different BIOS than it is supplied with and say bye bye to your warranty. Last time I tried rma'ing a card that I had flashed, Gigabyte refused warranty service.