thank you very much for the reply,the link is the following:
https://rog.asus.com/forum/showthread.php?88571-7970-Matrix-Platinum-Fan-Control-Only-1-works-GPUTwe...My configuration is:
Motherboard Gigabyte m68mts2 3.1
ram 8gb kingston 1600
Psu vultech gs850r 850w
i have tried several gpu tweaking utility,but the second fan stays always at a low rpm,15/20%.
with the latest asus gpu tweak,the slider of the second fan makes no effect on the fan,and the tabs "Auto/Manual/User define" are gray and are unusable.
with the 7970 dcu II top i have no problem to regulate the fan.
the button on the pcb for the 100% works normally.
Maybe the second fan starts to work when the temperature rise over a certain level?