I am using dd-wrt with the archer C9, and it shows the temperature sensors form CPU and WIFI cards. CPU easily reaches 80 celsius degrees, So i decided to use a small 12v fan connected to one of the USB ports in the rear, just in the middle, using USB 5v output. It spins really slow without noise but the temperature is now on 50 celsius degrees. The used broadcom processor could work without issues near 100 celsius degrees.