This is the design and implementation of the scoreboarding algorithm for a subset of MIPS in software. The scoreboarding simulator accepts as input a text-file containing MIPS assembly and output the completed instruction status table showing the clock cycle of Issue, Read Operands, Execute Complete, and Write Result. We will utilize four distinct functional units: integer, mult, add, and div. In order to configure the system, we will use an assembly directive to define the number of each functional unit and the latency.
Here is a sample ASM file that the simulator would be able to read (see decode.py for all accepted instructions):
.integer 1 1 ; one int unit that operates in 1 clock
; (execute complete the cycle after read operands)
.mult 2 10 ; two multiply units that take 10 clocks
.add 1 2 ; one add unit that takes 2 clocks
.div 1 40 ; one div unit that takes 40 clocks
LD F6, 34(R2)
LD F2, 45(R3)
MULTD F0, F2, F4
SUBD F8, F6, F2
DIVD F10, F0, F6
ADDD F6, F8, F2
The simulator contains three important files:
- scoreboard.py defines the Scoreboard class and the ScoreboardParser class which are used for the scoreboarding algorithm and parsing the asm file respectively
- fu.py defines a generic functional unit, which has properties for the type and number of remaining clocks
- decode.py contains the Instruction class which describes an Instruction object within the scoreboard. It also provides methods for decoding an instruction string from the asm file and producing an Instruction object
Compiling and running the file is easy. It can be done with the following command
python scoreboard.py
To choose a different asm file, open up the scoreboard.py class and change the ASM_FILE property at the top.
NOTE: python in this case assumes python3