zuldan wrote on Yesterday, 21:08:
My Asus ProArt PA248QV works great. It auto switches to 4:3 as long as the signal is coming through the HDMI port.
Does it do so even in DOS, when displaying 320x200 mode 13h (line doubled to 640x400 by the VGA card) ? AFAIK, it does NOT.
Many monitors, including that specific one, AFAIK, only treat as 4:3 resolutions whose active pixel counts for the x and y axes have a 4/3 (1.33) ratio. I.E. 640/480=1.33 , so the monitor will "see" it as 4:3 , but 640/400=1.6 , so the monitor WILL NOT display it as 4:3. In other words, the monitor will assume that all modes have square pixels AND "deduce" the aspect ratio from active pixel count ratios for x and y axes, which does not work for 320x200 because it does NOT have square pixels.
You will not have encountered that issue IF you use the native HDMI or DVI output of most (probably all) Nvidia and ATI based video cards because, by default, those video cards, in DOS, upscale 320x200 mode 13h to a 4:3 square pixel mode resolution that is then pillarboxed into a 16:10 resolution (exact resolution will depend on monitor EDID and VGA BIOS logic, but often the monitor's native resolution), so the black bars on each side of the image will be generated by the video card.
If one uses a VGA card's analogue output and digitizes it with an OSSC, the resulting 640x400 resolution, sent over DVI/HDMI, will require a monitor that allows forcing 4:3 mode to have a proper 4:3 aspect ratio, which the PA248QV cannot do (unless newer revisions/monitor firmwares have added that feature), but the 252B9 and a few other monitors can do.