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