emulation in 1080p

[vsub_]

If the "Rendering Resolution" is set to Auto,ppsspp will set the rendering resolution accordion to your window size and since full screen is even higher than maximized window,ppsspp will need even more power from your gpu.

Just because your screen resolution is 1920x1080 doesn't mean you HAVE to use 1920x1080 as a rendering resolution,you may even not notice any difference in the image quality when you switch between higher rendering resolution modes.
So try from lower to higher and see which one looks good enough(using higher than that will just lower your speed)

My screen resolution is 1024x768 and 2x looks more than enough.