I have a monitor plugged to my laptop using a HDMI to USB adapter. When using this adapter, Allegro runs very slowly. It seems that it is not using my video card.
Is this a known issue with a workaround I can try?
Not an engineer but I've repaired machines. When you have HDMI or DisplayPort generated, you typically can't go back to a low-speed transport like USB. But, USB-C and Thunderbolt can carry digital video signals and up to 100w of power. The video mux chip is a common blown part when people spill liquids into laptops, routes video data from a built-in GPU on the main CPU or from an NVidia GPU.
Not proud of it. But, I help my coworkers diagnose this problem by opening a design in Allegro, launch the 3D canvas. Open the Windows Task Manager and System performance. I'm running Allegro 17.4 sp 23 at the moment. Panning around the Allegro design or spinning the model in 3D canvas definitely uses the Nvidia GPU on my HP Z2 G4 mini with Nvid P1000 (love this machine. No battery backup like a laptop but it loads in a backpack nicely.)
In the Windows control panel, >System, then under Display settings.
Then >Graphics settings.. Under Graphics performance preference (I think you need Allegro running to change this. Otherwise Solidworks would feel left out..)