Solved mystery of GPU stuck at full speed in 3D. I have EVGA GTX 570 on w/c, BIOS 70.10.49.00.74 and dual 22" monitors.
It's a shame really, because GPU will stuck on full 3D mode as there is apparently a hardware limitation:
GPU Runs at a High Performance Level (full clock speeds) in Multi-display Modes
This is a hardware limitation and not a software bug. Even when no 3D programs are
running, the driver will operate the GPU at a high performance level in order to
efficiently drive multiple displays. In the case of SLI or multi‐GPU PCs, the second GPU
will always operate with full clock speeds; again, in order to efficiently drive multiple
displays. Today, all hardware from all GPU vendors have this limitation.