When it is 400msec it looks like the whole page with full text scrolls pixel-by-pixel without any jump. It was smooth but slow in the sense that, it looks like for my small screen of 128 pixels height, it is going to take 400*128msec to scroll the whole page.
How the animation time is measured? When it is 400msec, does it mean it can scroll one page across in 400msec even for higher resolution e.g. 480*272?