26
Creating a Single Datapath
•Data path segments for
–Fetch
–Execution
• Arithmetic operations (R-type instructions)
– Register file (read), ALU, register file (write)
• Load/store
– Register file (read), ALU (effective address), data
memory (read/write), register file (write on load)
• Branches
– Register file (read), ALU (comparison), Adder
(branch target address), PC (update)
•Can we combine these segments so they are shared?
27
Creating a Single Datapath
•Yes!
•A simple datapath
–Execute instructions in a single cycle
–Hence, no datapath element used more than once
by an instruction in a single cycle
• Any element needed more than once: must be duplicated
–Share datapath elements among different
instruction classes
