EEE230 Pipelined Datapath and Control Practice problems
Use this bit of code for these questions add $5, $7, $2
sw $9, 4($6) lw $4, 8($12) or $6, $5, $3
1. This question focuses on the content written to the internal or pipeline registers.
Assume that the code is stored starting at 0x00600000, the values in the memory are all initially -1, and the register values are the same as the number (so $5 holds the value 5).
Using the pipelined diagram, give the contents of the value(s) written to each internal register (as indicated) at the end of the 4th clock cycle. Be specific and give the actual values placed into the register.
Remember that even if the instruction will not use the value, there is no control on writing to the internal registers.
a. IF/ID
PC = ?
b. ID/EX
PC = ?
Read data 1 = ? Read data 2 = ? Sign Extend = ?
c. EX/MEM
PC = ?
Read data 2 = ? Zero = ?
ALU result = ?
d. MEM/WB
ALU result = ?
Read data = ?
2. This question focus on the values of the control written to the internal registers.
For the code, complete the control as it would be stored into the ID/EX, EX/MEM and MEM/WB registers at the end of clock cycle 4.
a. ID/EX
RegDest
ALUSrc MemtoReg
RegWrite MemRead MemWrite Branch ALUOp
b. EX/MEM MemtoReg
RegWrite MemRead MemWrite Branch
c. EX/MEM MemtoReg
RegWrite
PC = 0x00600010 b. ID/EX
PC = 0x0060000C
Read data 1 = 0x0000000C Read data 2 = 0x00000004 Sign Extend = 0x00000008
c. EX/MEM
PC = 0x00600018
Read data 2 = 0x00000009 Zero = 0
ALU result = 0x0000000A
d. MEM/WB
ALU result = 0x00000009
Read data = 0xFFFFFFFF
2.
a. ID/EX
RegDest 0 ALUSrc 1 MemtoReg 1 RegWrite 1 MemRead 1 MemWrite 0 Branch 0 ALUOp 00
b. EX/MEM MemtoReg X
Answers
1.
a. IF/ID
RegWrite 0 MemRead 0 MemWrite 1 Branch 0
c. EX/MEM MemtoReg 1
RegWrite 1