Update 7:

Finally OFFICIAL NVIDIA info on the subject:

"In response to Issue #1 -- fan turns off in 2D mode and when running some 3D apps (such as screen savers and a few other applications).

All production GeForce FX 5800 Ultra's do this. This is the most extreme definition of "Silent Running"....it is truly silent. We did this to improve the user experience for 2D and screen savers. We also adjust the core and memory clocks as well as voltage levels to make the FAN-OFF operation safe for the chip and other components on the board. During FAN OFF mode, the temperature of the GPU may rise to 100+ degrees C. This is fine and is well below the safety limits for the device. The device can actually run at 140 degree C without damage.

Issue #2 -- Two Gainward cards have shown screen corruption when operated in FAN OFF mode for an extended period and then switched to FULL 3D mode.

As before, NVIDIA cannot duplicate this. This board does not use the NVIDIA FX Flow thermal solution, so the details of fan operation and temperature may be different than that of the NVIDIA FX Flow. Of course, an end user should contact the board vendor of the product if it shows screen corruption during normal, within-spec operation."

While PC Ekspert team still feels its not risk-free to have a card that reaches 100C in your system, at least you know your FX Flow card won't die. Its more likely its heat will burn some cable or an adjacent card will heat up nicely and glow in the dark... Seems FX Flow is over engineered a bit. The card can operate at insane temperatures - so why use FX Flow at all? NVIDIA could just have used an ordinary fan/heatsink and save all of us lot of noise.

On the other hand, if you are owner of a Gainward card, you are in trouble! We wonder how many other vendors make cards that don't use FX Flow thermal solution and suffer from the same problems (we are sure Gainward is not the only one...). NVIDIA also told us that they are working with Gainward on this issue. It seems we now have to wait for info from Gainward about the whole thing!

Update 6 - It seems problems can be reproduced with Cg examples

A reader from Italy mailed us today and told us we should check Cg examples from NVidia "The Cg Tutorial: The Definitive Guide to Programmable Real-Time Graphics". He tried running 'C7_refraction' example and the fan would stop running after some time. You can download these examples from: http://developer.nvidia.com/view.asp?IO=cg_tutorial_software (17590Kb). The card he uses is ASUS V9900 Ultra/TD.

As we currently have no FX5800 cards (we had to return the one we had) we can't try it out right away. I am sure we will get another card in few days but until then our hands are tied.

As you know, NVIDIA promised answers three weeks ago, but since then they have been ignoring us, and there have been no driver updates. Speaks a lot about how much they care about owners of their flagship FX5800 cards.

For previous article/updates about GeForce FX5800 cooling problems, click here.