linux 4.11.4

I use the IGPU on SKL and a RX460 as a dedicated card. In XOrg i turned
autobindgpu, autoaddgpu off and singlecard on. with fb fbcon=map kernel
parameter i map the linux ttys to different cards. the way i switch to the AMD
card is to vt switch and then change the input on my monitor. this works fine
and lets me login via agetty and launch a new xserver. One thing i noticed is
that until i actually do that the memory clock of the card stays high (17xx
mhz?) which makes it 5-8°C hotter and probably uses more power than it needs.