   Swap chains
  a little qs about swap-chains presentation interval.Regarding D3DPRESENT_INTERVAL_IMMEDIATE. the msdn mentioned that will attempt to provide an unlimited presentation rate. does this mean that the backbuffer will be updated multiple times during a single VSync , wouldn't this be a little disturbing to the motion on the screen.   
  It means the buffers will be swapped immediately, as soon as they're ready. This doesn't disturb the v-sync.Dave   ;  so the pointers are swapped , doesn't the front buffer need to wait till the VSynce is over to be presented to screen?   