I have an Asus 4850 and followed the instructions using Winflash. It didn’t work for me. The card would wig out (black screens) and the fan settings wouldn't hold in Linux.
Someone suggested I try flashing with ATIFlash instead. The problem was that ATIFlash runs in DOS from floppy. I have no floppy, so I had to set up floppy emulation on a USB key. That took a couple of hours to figure out and get working. Also it was suggested that I use the MSI BIOS as a reference for the Asus. The MSI has a low power mode of 160/500 for example. Anyway, once I got all that sorted out, I was able to flash my card and it worked perfectly. The settings work in Vista and Linux also the card runs cool even under load. I'm happy.
