I want to buy a GTX 1080 card for my Z640 workstation.
kcspkd, you can install and use a GTX card such as the GTX 1080 in your Z640 without any problems. GTX cards work as a charm in any Z4xx/Z6xx/Z8xx workstation. I have a GTX 760Ti in a Z800 and a GTX Titan X Pascal in a Z440.
