are you sure you are using the same mode for both ums and kms? The regs seem to indicate that ums is using 1280x800. check xrandr and make sure you are using 2560x1600 for both ums and kms and then dump the regs.
are you sure you are using the same mode for both ums and kms? The regs seem to indicate that ums is using 1280x800. check xrandr and make sure you are using 2560x1600 for both ums and kms and then dump the regs.