That's correct, you need to patch the driver with the pixel patcher to bypass the signature check with a modded bios. The Bios info will not change in GPU-Z. Once the card shows up in Device Manager without errors, you can overclock and undervot it using Afterburner before starting the miner. Somewhere around 1150 MHz for the core clock and 2075 MHz for the memory clock with a -98 mV undervolt should get you to 28 MH/s. Also use HWinfo to check for memory errors once you overclock it.