...but it's still unclear to me if someone could get a modified BIOS's fan profile to work below 30%.
Obviously the usual caveats apply with graphics card BIOS flashing, including following the instructions carefully and being aware of the risks, but that said I have modified the BIOS for an nVidia 6xx series card successfully using Kepler Bios Tweaker 1.25 from this source
. (The download is in RAR format, if you don't have anything that works with this format then 7-ZIP
will unpack it.)
The procedure was (1) Save original BIOS using GPU-Z (2) Using Kepler Bios Tweaker and a copy of original BIOS file change the minimum fan percentage from 30% to 25% (3) Flash the card with the modified BIOS using NVFlash. A graphics card utility verified that the change had taken place. What difference it makes will depend on the fan profile of the stock cooler. Typically PWM fans do not run at 0 rpm at 0% duty so the profile may set the minimum speed to apply to the 0 to 30% range, or maybe 0 to 25% or 0 to 20% and so on. It will depend on the card but potentially a BIOS mod may make little or no difference.