I'm using AMD's RX 480 graphics card. I have figured out how to resolve the sluggish Win10 operating system performance when v11.3 is launched as well as how to increase mining speed. Just specify "-dmem 0 " to disable the default "twice more GPU RAM" mode. Miraculously the mining speed rises to 568 H/s from 276 H/s. Also the whole Win10 system is no longer sluggish and becomes normal. Thank God.