Thanks to David Christensen over on debian-user mailing list: Your E6520 is a hybrid laptop with two chipsets: one Intel graphics, one Nvidia. On battery power, it will use the Intel, when plugged in to higher resolution displays or whatever, it will use the Nvidia.
This is also similar to high end gaming laptops. With the standard install, it's occasionally possible that conflict between which display chipset to use / nouveau drivers may mean lock-ups. There are three solutions possible, I think [I no longer have one of these to deal with] 1. Ignore the Nvidia and use the Intel driver only. This will probably work to some extent. It may be necessary to deny list the Nvidia drivers 2. Ignore the Intel and use the Nvidia drivers only - probably the non-free drivers 3. Use the Optimus drivers which will allow the laptop to switch between chipsets. This is provided by the bumblebee package in Debian - and there are two types: one is a fully free driver and links in with nouveau, one relies on the Nvidia proprietary drivers. In my limited experience: It is easiest to start with an expert text mode install and explicitly uncheck/deselect the graphics drivers as you go: uncheck Debian graphical environment and Gnome. Install only the standard packages and minimal drivers - command line only. Install build-essential and dkms packages and also choose which bumblebee package to use and add it. If you choose to use the proprietary drivers - build them at this point with no major graphics drivers loaded. The proprietary drivers will taint the kernel. dkms - if properly installed - should build the necessary kernel drivers with each kernel change. At that point, everything should work on the command line. After that, reboot and as root/sudo equivalent, use the tasksel command to install a desktop environment. This _should_ allow everything to work correctly. Hope this helps. With every good wish, as ever, Andy Cater
