Bronya, thanks for your great work!!!
Following your instructions I have now got my sapphire 256mb PCI x1950pro working with kalyway 10.5.1. I have QE/CI, resolution changing and no mouse tearing but one small problem remains. I am driving my monitor, a Samsung TFT, via DVI and every so often it seems to lose sync. leaving me with a blank screen. If I wait a few seconds then sync. is regained for a short while before the same thing happens again. I also see some screen judder. If I try and drive the monitor at 75Hz instead of 60Hz it loses sync much more often.
I know there is not a problem with the hardware as I never see any of this whilst just running XP. Any ideas what this is and how I can stop it?