Comment # 11 on bug 941931 from Jan Matejek

(In reply to Michael Chang from comment #10)
> Looks to me that the video ram is too small to enable page flipping by
> swapping poiners of on-screen and off-screen buffers in video memory to
> update the screen quicky [1]. 

this is true, but doesn't help the issue

indeed, lowering to 1600x1200x32 (6400 line width, 15MB used) gets rid of the
line-by-line rendering, and the whole image appears at once

BUT, there is still roughly the same delay before the image appears

so ISTM it's the filling of the buffer itself that is causing the slowdown