Yes, software scaler works basically with only low resolution. Using my build, try a parameter -forcescaler to force the scalers work in any resolution. (only normal/rgb works, however)

Thanks ykhwong. But it leaves me curious as to why the scalers are not forced in all situations? If I put it in my config, then it is because I 1) want a bigger window, 2) possible some smoothing of the results. I don't like DOSBox/the scalers to ignore my requests.

Some high resolutions like 1024x768 may require lots of reosurces if scalers are always forced in any res, and some people may dislike it due to a decline of speed or unsupported, too high resolution (e.g. Normal2x : 1024x768 * 2 = 2048x1536.)