Well i Own XPS 15 z in Qatar. when i install below mentioned driver on my Win8 my computer reboots, saying an error occured trying to fix. but i think it doesnt fix. i still get ! for USB-IF xHCI USB Host Controller.
JMB389 Card Reader driver: http://dell.to/13udJ0Z
Also my screen sometimes flickers on 60hz ? any workaround ??