adapter?
lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cedar [Radeon HD 5000/6000/7350/8350 Series]
vi /etc/apt/sources.list
# Debian 8 "Jessie"
deb
http://httpredir.debian.org/debian/ jessie main contrib non-free
apt-get update
aptitude -r install linux-headers-$(uname -r|sed 's,[^-]*-[^-]*-,,') fglrx-driver
aticonfig --initial
reboot
c
https://wiki.debian.org/ru/ATIProprietary#configure