Others have recognized the need to re-examine page replacement algorithms in large memory machines. Wood and Katz argued for getting rid of the modified bit [ 171, though we do not necessarily agree with their conclusions. Harty and Cheriton [18] describe an interface exported by the VM system to extemal pagers that can be used to control physical memory. Harty and Cheriton recognize that future computers will have giga-bytes of memory and advocate providing more control over memory to extemal pagers. (They also state that their interfaces are useful for providing support for multiple page sizes, though we believe that the interfaces they propose are not sufficient for that purpose.)