Looks like the Zalman on this card is parked at a fixed speed, no matter the temperature. If you actually OWN or use this card, can you speak to any fan fixes in terms of having it slow down under 2D and speed up in 3D?
More to the point, is there a hardware limitation, or is it all software?
You can't do it with software as the the cooler has only three wires, no PWM is possible (idiotic solution). I've just ordered a Zalman Fan Mate 2 (8 $ or so), I hope it will do the job -- it is a simple potentiometer anyway.
Well I can vouch for the other Sapphire custom cooled HD 4850, the Dual Slot edition. Even though the cooler is not as effective as the one in the toxic version, it does have a default setting of around ~15%, but as heat increases it has risen up to 45% so far (GPU doesn't get beyond 60 C, so I don't think it has a reason to increase any higher).
Zalman Fan Mate 2 is not the best way, because the VGA fan's connector is a miniature one and does not fit into the Fan Mate 2 directly. I set it apart and finally could connect to Fan Mate 2, but it requried some DIY (half an hour for me). It's important that you need a three pin fan connector on your mobo too. At the end my system is much-much quieter, so it was worth it.