There is no PowerVR involved here, it is "PVR" as in "Personal Video Recorder" (also known "DVR"). It's a TV encoder card, that just happened to sit in the test machine.

I just expected it not get accessed by SteamOS at all. It seems, that some "Plug & Play" automatisms got out of control...

The test machine itself of course fulfills Steam's requirements with a quad-core AMD64 CPU, 8 GB RAM and a 512 MB nVidia card.

After logging in with "steam" user for the first time, GNOME presents me this message:

Oh no! Something has gone wrong.

A problem has occurred and the system can't recover.
Please log out and try again.

The reason was the ivtv/cx2341x driver loaded automatically for a PVR card installed in the test system. The driver crashes with a kernel oops, because of missing (non-free) firmware. So two questions arise:

1. Why does the SteamOS kernel include a (broken) driver for that thing anyway and is loading it automatically?

2. Why does GNOME try to access a PVR card on login and crashes?