After having issues with the HDMI expansion card on my FW16 and Ubuntu 22.04.4, I discovered that the card does not work properly in one of the three slots that are supposed to support it. Using the slot numbers from this KB article, display cards are supposed to work in slots 1, 2, and 4, but my HDMI card only works in slots 1 and 2.
If I put the card in slot 4 and plug in a display, the desktop environment and Gnome’s display settings act as if the display is working (including showing the name and resolution of the display), but the display receives no signal. If I leave the display plugged in for a couple minutes, the image will intermittently appear for about a second at a time before the display loses the signal again. In one test it took over a minute before the image appeared for the first time.
I looked at dmesg and saw errors like those described in this post, but the errors occur whether I plug the HDMI into slot 4 or into slots 1 and 2. The exact set of errors varies between instances of plugging the card in; I’d have to test it further to see if the messages vary in a consistent way between slots 1/2 and slot 4. I did confirm that the HDMI adapter consistently appears in the output of lsusb even when the card is in slot 4 and the display is receiving no signal.
I tested slot 4 with the USB-C (for charging), USB-A, and audio cards, and all of them worked without any intermittent failures.
