There are old games with resolutions like 640x480, 800x600 where the pixels appear blurry when scaled up - or the video from the game is to small, when "scaling-mode" is set to "center".
"Center" mode is like 1:1 -1 pixel corresponds 1 pixel. So there is a black frame around the screen.
It would be great if there were also modes like 2:1, 3:1, etc. Or scaled up automatically. Also with black frames around.
For example 640x480 scales up to 1280x960 on FullHD monitors, or 1920x1440 on QHD monitors.
(below, the game "Heroes of Might and Magic" from 1995 - open up in new TAB to see the aliased scaling method)