Tomasulo's algorithm Example

This is a example dlx code ex3.s for tomasulo's algorithm simulator.



A:      .float 2.0
        .global B
B:      .float 1.0
        .global C
C:      .float 0.0

        .align  4
        .global _main
_main:
        ld      f6, 256(r1)
        ld      f2, 260(r2)
        multf   f0,f2,f4
        subf    f8,f6,f2
        divf    f10,f0,f6
        addd    f6, f8, f2
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        trap    #0

Execute tomasulo's simulator


(yueh) ~/dlxsim % dlxsim -TOMASULO
(dlxsim) stats hw

Memory size: 65536 bytes.

Tomasulo's Algorithm Hardware Configuration
 3 add/subtract units, latency =  2 cycles
 2 mult/div units,     latency = 10 cycles (multiply)
                       latency = 40 cycles (divide)
 6 load_units,         latency =  2 cycles
 3 store_units,        latency =  2 cycles

Load sample code


(dlxsim) load ex3.s

Use step execution


(dlxsim) step
stopped after single step, pc = 0x4: nop
(dlxsim) step
stopped after single step, pc = 0x4: nop
(dlxsim) quit
(yueh) ~/dlxsim % dlxsim -TOMASULO
(dlxsim) stats hw

Memory size: 65536 bytes.

Tomasulo's Algorithm Hardware Configuration
 3 add/subtract units, latency =  2 cycles
 2 mult/div units,     latency = 10 cycles (multiply)
                       latency = 40 cycles (divide)
 6 load_units,         latency =  2 cycles
 3 store_units,        latency =  2 cycles
(dlxsim) load ex3.s
(dlxsim) step _main
stopped after single step, pc = _main+0x4: ld f2,B(r2)
(dlxsim) step
stopped after single step, pc = _main+0x8: multf f0,f2,f4
(dlxsim) step
stopped after single step, pc = _main+0xc: subf f8,f6,f2
(dlxsim) step
stopped after single step, pc = _main+0x10: divf f10,f0,f6
(dlxsim) step
stopped after single step, pc = _main+0x14: addd f6,f8,f2

Print scoreboard content


(dlxsim) stats tomasulo


                      TOMASULO's         5 th clock cycle
  Instruction         Issue          Execute       Write Result  
+============================================================================+
         ld f6,A(r1)    V               V               V 
         ld f2,B(r2)    V               V                 
      multf f0,f2,f4    V                                 
       subf f8,f6,f2    V                                 
      divf f10,f0,f6    V                                 
+============================================================================+

     Name   Busy     Op         Vj         Vk        Qj       Qk  
+=======================================================================+
    add1     YES     subf      (f6)                          load2  
    add2     NO    (null)                                           
    add3     NO    (null)                                           
    mul1     YES    multf                 (f4)      load2           
    mul2     YES     divf                 (f6)      mul1            
+=======================================================================+

      F0      F2      F4      F6      F8      F10      F12     F14  
+----------------------------------------------------------------------+
Qi   mul1    load2                   add1     mul2                   
Busy  YES     YES     NO      NO      YES     YES      NO      NO  
+======================================================================+
     F16     F18     F20     F22     F24     F26     F28     F30
+----------------------------------------------------------------------+
                                                                   
Busy  NO      NO      NO      NO      NO      NO      NO      NO  
+======================================================================+

go to trap


(dlxsim) go
TRAP #0 received

Dump information


(dlxsim) stats tomasulo


                      TOMASULO's         54 th clock cycle
  Instruction         Issue          Execute       Write Result  
+============================================================================+
         ld f6,A(r1)    V               V               V 
         ld f2,B(r2)    V               V               V 
      multf f0,f2,f4    V               V               V 
       subf f8,f6,f2    V               V               V 
      divf f10,f0,f6    V                                 
       addd f6,f8,f2    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
                 nop    V               V               V 
            trap 0x0    V               V               V 
                 nop    V                                 
+============================================================================+

     Name   Busy     Op         Vj         Vk        Qj       Qk  
+=======================================================================+
    add1     NO    (null)                                           
    add2     NO    (null)                                           
    add3     NO    (null)                                           
    mul1     NO    (null)                                           
    mul2     NO      divf     (mul1)      (f6)                      
+=======================================================================+

      F0      F2      F4      F6      F8      F10      F12     F14  
+----------------------------------------------------------------------+
Qi                                            mul2                   
Busy  NO      NO      NO      NO      NO      YES      NO      NO  
+======================================================================+
     F16     F18     F20     F22     F24     F26     F28     F30
+----------------------------------------------------------------------+
                                                                   
Busy  NO      NO      NO      NO      NO      NO      NO      NO  
+======================================================================+

Quit the program


(dlxsim) quit

Since we can't use integer operation in this simulator, there is a skill which we can load values for registers.



        ld      f6, 256(r1)
        ld      f2, 260(r2)

The 256 means the first data location. Because float needs 4 bytes to store, the next value is 260. The other choice is to use put or fput to store values, then use get or fget to look up values.

Last Updated: 1995.5.20