For me, I don't think it's memory. I am not even doing "renders", I just have the Viewport set to NVIDIA Iray. I have a scene right now where I have reproduced the "OptiX Prime error" 3 times. If I save the scene with Optix Prime Acceleration checked, then restart DS, open the scene and I get the error right away. Likewise, if I save the scene with Optix Prime Acceleration unchecked, then restart DS, open the scene, I do not get the error. According to GPU-Z it's only using 1.78G of memory (when it's working). My card is 4G. The only thing that bugs me is that I don't remember seeing this same error when I was trying to figure this out a few months ago.