Comment by Zelizz

My very-rough feeling about it from playing around with Stable Diffusion is that it takes about 4x as long if it runs out of GPU memory and needs to shuttle data back and forth from system memory. There are a lot of variables though - on my 3070 with 8GB of RAM, I can get very impressive 512x512 images in about 10 seconds with somewhat low sample counts, or I can set it to a higher resolution and sample count with 2x upscaling and get a really sharp image in around 2 minutes.