4K (RPi 4B 4GB) performance?

[lderossi]

I just set up a brand new RPi 4B w/ 4GB, latest Buster 32bit img, updated all packages (and got all required support pkgs) and installed Pi3D. Connected to a 4K TV (happens to be rotated into portrait via xrandr, but doesn't seem to matter), and I use xinit to launch the demos. All run at low single digit frame rates, including the simple blend fade on PictureFrame2020.

Is this typical of 4k performance? If I force resolution down with xrandr it gets better but still not quite what I'd expect from what I've seen in others' 1080p examples.

I've upped gpu mem to 256MB, using KMS/FKMS, lowered all PictureFrame2020config settings (disabled auto resize, tried fps settings of 5-90, turned off blurring, etc), and nothing seems to change the low display fps.