I did it with great success...
I have a Sapphire 9500 pro purchased about 4 months ago. I used the
Warp11 bios to flash the card...after flashing the bios using a floppy disk, I rebooted and Windows recognized the card as a 9700 pro. After reinstalling the drivers, I then overclocked the card to 9700 pro levels...and after 4 months, the card has remained rock solid and stable. By flashing the bios, you enable the 4 rendering pipelines that are disabled...and allow the card to be overclocked. The memory bandwidth is still limited physically, but for the most part, the card works and acts like a 9700 pro until you reach the higher resolutions...which is where it becomes limited.