exception if you know your bios version number, and the modded bios version exactly the same !!!
When ppl doing this mistake , they coming back to this forum and keep asking why my rig froze up all the time , why my cards hashing speed going down , why my pool side reporting is much lower than what my mining software telling me ...
What are the advantages of doing it?
There is a lot of advantage to modding ur bios , but you need to know what you doing , most ppl calling bios mod , when they changing mem straps in any bios editor software
thats not the real bios modding 
Advantage with a properly modded bios , fine tuned cards :
- Much less power consuption
- Much higher hash rate
- lower gpu temperature
- lower card temerature , slower fan speed , quieter rig
- less heat on components
- longer hardware life
Disadvatge :
- you can say good bye to your warranty
