page exception requesting page aaa and an indication as to whether the page exception initiating client client a in this case has reported forward progress the host interface 104 sends the virtual address of the missing page page aaa to the central processing unit 103 furthermore the host interface 104 also sends a forward progress bit to the central processing unit 103 if and only if client a reported forward progress if the central processing unit 103 receives the page fault virtual address but does not receive a forward progress bit the central processing unit 103 interrogates the frame buffer memory 60 to determine which pages are available for swapping however in accord with the principles of the present invention the central processing unit 103 does this in a particular way when a client causes a page fault exception because that client say client a 52 needs a page say page aaa see fig1 but that client does not report forward progress the central processing unit 103 adds page aaa to a page list 402 see fig4 furthermore since page aaa must be in the frame buffer memory 60 for client a 52 to make forward progress page aaa is tagged as a required page using an associated tag list 404 servicing the page fault exception is then performed by swapping one of the pages that is not required that is does not have an accompanying tag in the tag list 404 say page ghb.