Operating Systems Memory-Mapped 1/0(2) Two address One address space Two address spaces OxFFFF Memory 1O ports 0 (a) (a)Separate 1o and memory space(IBM360) w Each control register is assigned an lo port number H Address spaces for memory and 1/O are different (b)Memory-mapped l/o(PDP-11) w Map all the control registers into the memory space H Each control register is assigned a unique memory address to which no memory is assigned (c) Hybrid(Pentium) H Memory-mapped 1/O data buffers, separate IO ports for the control registersOperating Systems Gao Haichang , Software School, Xidian University 9 Memory-Mapped I/O (2)  (a) Separate I/O and memory space (IBM 360)  Each control register is assigned an I/O port number.  Address spaces for memory and I/O are different  (b) Memory-mapped I/O (PDP-11)  Map all the control registers into the memory space.  Each control register is assigned a unique memory address to which no memory is assigned.  (c) Hybrid (Pentium)  Memory-mapped I/O data buffers , separate I/O ports for the control registers