Thanks Ged and Dave. Turning off native canvas functionality did the trick.
> . . . puts more functionality into the GPU
Off to look for the least $$$ DirectX 12 vid card to add to this system.
[ Like many PS users, I don't use fancy GPU-driven features, so don't need fancy card with fancy performance. Just do simple image processing and composite layering ]
I think we will find more and more core functions moving toward the GPU as we go forward. It makes sense in order to speed up processing on the larger images we take for granted today. That does not mean you need a high end GPU, but do make sure any new card meets the recommended system requirements I linked in terms of Direct X and VRAM.
Intel HD Graphics 4600 is an integrated GPU (built into the CPU) released in 2013. The new version of Photoshop puts more functionality into the GPU for which your GPU which does not meet the current system requirements.