Making full use of memory on graphic cards

Question

Onboard graphics cards often reserve some of the system main memory for their own use.

For a computer with a separate graphics card which has its own memory, is this possible that some of it be borrowed and used like system main memory?

Running typical desktop applications normally require much more system main memory than memory on the graphics card. If the OS is smart enough to dynamically allocate some of it when it's low on main memory and release it back to the graphics card when necessary, this will be great.

Answer 1

It is possible to use some of it as swap or ramdisk under Linux, but most operating systems do not allow this.