for example, this is one of the possible ways that i supposed, not sure if its efficient or not. assume that the game is using 320*200*256color mode:
1. set up 2 pages of 64kb framebuffer in video ram.
2. render a frame of 320*200 image in system ram.
3. copy the image to video card framebuffer page 1. (shall the program stop anything else and just wait for the bus to transfer all this 64kb data? or can it make any use of dma controller?)
4. set the video card to display page 1.
5. render another frame in system ram.
6. copy the image to video card framebuffer page 2.
7. set the video card to display page 2.