Neither xf86-video-fbdev nor xf86-video-fbturbo exist in Tinycore, so unless you compiled them yourself, you must be using something else.
When testing freerdp with Xorg-3d and one screen, I found using /gfx-h264:AVC444 increased the speed - since xf86-video-fbturbo stops Xorg-3d acceleration from working, I suspect you would be better off without it.