r9 290x Bios

The best Video BIOS for a Video card is the one it shipped with.
It's very rare that a manufacturer releases a Video BIOS update for a card, updates for the AMD R2xxX series mostly fixed automatic fan settings to remain within the TDP limits while maintaining full clock speed at temperature.

What most people don't realize is that a Video BIOS is meant to be used exclusively for a very speficic card and the specific PCB revision of it.
Blindly flashing cross-brand files onto a card is about the worst idea someone could have, this is just begging for trouble.
Especially since the R2xxX series is specifically walking an extremely fine line between TDP, Temperatures, Fan power setting, Clock and Voltages. It took the manufacturers months of time and several iterations of settings to achieve the optimum desired performance output, effectively causing the initial shipment delays.
Fiddling around with these would be extremely challenging at best since this generation of GPU just has too many variables to take into the performance equation.

The absolutely only reason to flash a card with a modded BIOS would be after very carefully discovering its minimum voltage/maximum clock (sweet spot) for a single purpose, modding the table entries yourself and having the intention to make this change permanent. Good luck with that with multi-factor auto-throttling GPUs already designed for redline TDP limit operations.

Just as important it is to save the original Video BIOS to disk, in case something goes wrong or the card is re-assigned to normal duties (i.e. before reselling).