After i saw OS getting it to 110 C, i took it out, cleaned it and the whole case thoroughly, took off the GPU cooling and applied new coating of thermal paste. I even added one more case ventilator to blow out hot air and enabled the front one to bring more extra relatively cooler air inside.
That did not help at all. For OS.
Have you tried to manually increase the speed of your GPU fan?
Maybe your tool is giving your wrong information? Would be worth a double check with for example MSI Afterburner/Rivatuner. There is also a free tool available (MSI Kombustor) that can be used to benchmark your GPU. It puts a 100% load on the GPU. If your card reaches more than 90-100 ｰC here as well, there is something severly wrong with your hardware/cooling.
My Radeon HD7870 never gets hotter than 75 ｰC, no matter in which game, D:OS included...
