Consider the single-cycle datapath with the following component ile and memories
ID: 3599434 • Letter: C
Question
Consider the single-cycle datapath with the following component
ile and memories have different latencies for latencies: (reads and writes.)
Functional Unit Time (ns)
Memory (read) 4
Memory (write) 12
ALU 8
Register File (read) 4
Register File (write) 7
a) Which instruction (add, sw, lw, beq) will take the most time to execute on t single-cycle
datapath, which components of the datapath will it use, in w order will it use them?
b) Calculate the cycle time for a single cycle datapath.
Explanation / Answer
a)
The maximum time will be taken by a add instruction as it will require register file read, register file write and the ALU computation. So it will take 7+4+8=19 ns.
The store instruction will have register read and memory write operation.4+12=16 ns
The load instruction will do register read, register write and memory read=4+4+7=15ns
The beq instruction will do register file read and write so 11ns.
So the add instruction will take the maximum time.
b)
The cycle time for a single cycle datapath will depend on the type of instruction getting executed on the datapath. We have the time required for each functional unit which can be used to calculate the time.