How to Turn off HDMI / power saving?

I have stability issues using the R4C+ headless, LAN, not WIFI

  • tried several distros, currently Dietpi
  • added eMMC to rule out µSD issues
  • tried different power supplies via USB-C, will try GPIO 5v next (my PI never draws more than 1,5A@5V)
  • I think this is the only Rock 4 that does not support USB 3.x PD…?!

checked with thermal imaging and I am surprised, where the heat is mostly present. in this order:

  1. Rockchip RK809-3 Power Mgmt front and backside of the Rock
  2. Radxa RA620-1 HDMI DP stuff
  3. CPU only under load

How can I turn off HDMI?
Do I need a heatsink on the PMU?


top left with the cross = PMU, top right at the USBC Port = HDMI


front