I've been trying to install Debian wheezy to a E525 Thinkpad Edge. This has an AMD chipset and a Radeon graphics card onboard. Install (from Net image) using amd64 works just fine but on first boot, the X windows is garbled/corrupts/speckled and unusable after the first reboot.
The problem is that the graphics card (Radeon HD6500D) needs the firmware-linux-nonfree package, but how to drop to a terminal to install it.
The easiest way to do it is to stop the kernel from attempting to modeset (this happens before X-windows starts). The usual way to see when this happens is when the boot messages change from a bigger font to a smaller font. We want to stop this from happening.
When the laptop boots, stop it at the grub prompt, and press e to edit the boot parameters
Press F10 to boot. Cntrl-Alt-F2 should bring up a terminal. Login as a user and su to root.
# cp /etc/apt/sources.list /etc/apt/sources.list.stock.yyyymmdd
Edit /etc/apt/sources.list and add non-free to the end of the line starting deb and ending "wheezy main". You do not need to add non-free to the security.debian.org lines.
My /etc/apt/sources.list line now looks like this:
deb http://ftp.uk.debian.org/debian/ wheezy main non-free
# apt-get update
# apt-get install firmware-linux-nonfree
Reboot and enjoy. You should not need to edit the grub parameters again. Note that the E525 also needs the firmware-realtek adding to it to get the wireless to work.