[理工] [計組] - 台聯大99

[skill91002 (有為)]

題目如下:

Given a MIPS instruction sequence shown below . Assume this code is executed

on a pipelined MIPS CPU with a five-stage pipeline, full forwarding, and a

predict-taken branch predictor. In addition, assume this CPU can finish the

register write in the first half cycle and the register read in the second

cycle.

               L3 :   add  ＄s6 , ＄s6   , ＄s5

                      addi ＄s5 , ＄s5   ,   2

                      slti ＄t0 , ＄s5   ,  10

                      bne  ＄t0 , ＄zero ,  L3

                      sw   ＄s6 , 100(＄gp)


(1) Assume the branch is taken , please draw the simple(traditional)

    multiple-clock-cycle pipeline execution diagram of the first 5 executed

    instructions, including all necessary stalls.

(2) If the branch is not taken, please redraw the simple(traditional)

    multiple-clock-cycle pipeline execution diagram of the first 5 executed

    instructions, including all necessary stalls.


請問這兩小題要怎麼寫比較好 ?



題目似乎沒有提到有無將 branch 之決定提前到 ID stage

第一題我的答案是這樣:

 L3 : add ＄s6 ,＄s6 ,＄s5    IF  ID  EX  MEM  WB

      addi＄s5 ,＄s5 ,  2         IF  ID  EX  MEM  WB

      slti＄t0 ,＄s5 ,  10            IF  ID  EX  MEM  WB

      bne ＄t0 ,＄zero , L3                *  IF  ID  EX  MEM  WB (EX 前饋給ID)

      add ＄s6 ,＄s6 ,＄s5                        IF  ID  EX  MEM  WB

想了一想前饋不是只有 EX->EX 或是 MEM->EX ?

有 EX->ID 的嗎?

感覺寫錯了



第二題就不會了

beq後面被沖刷部份不會描述



還請各位大大幫忙

謝謝!


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◆ From: 140.117.120.229
推 compulsory:full forwarding =>  EX->ID是允許的
→ compulsory:不過這樣講好像怪怪的  我想你的意思是EXE做完 到MEM才
→ compulsory:forwarding至ID
→ compulsory:而且好像也是在ID的地方會stall
→ compulsory:不是還沒抓指令就先stall
→ skill91002:c大的意思是要IF * ID EX MEM WB 這個順序嗎?