[simcop2387]

There's no current way to switch painlessly, but there is something that makes it slightly nicer than having to restart all of your programs. Check out Bumblebee [1]. It does it by running two X servers, one for the lower power system and another for the NVIDIA binary blob and plays with environment variables to get things working. Then it takes the NVIDIA server and copies the images over to the slower card. In a round about way it's what windows systems do for it, but not quite as sane and not quite as performant. There's been some work to create the sharing needed so that drivers can share the buffers directly and eventually there won't need to be the second X server. However this also depends on if that work either gets its license changed or NVIDIA GPLs the kernel bits to their driver.

[1] https://wiki.archlinux.org/index.php/Bumblebee