大家好 ,手邊有兩題有點疑問
台大電機 100
(10)Forwarding is a common technique th eliminate data hazard occuring among
pipelining instruction.
　　However,not all data hazard can be eliminate by forwarding.
Support on a particular machine,if an instruction following a load instr
-uction depends on the result of the load instruction,then a data hazard has
occured , and pipeline is stalled for one cycle
Which of following statements are not correct?
(a) In addition to data hazard,there can be control hazard in this
situation because we cannot determine the proper data to load
in the MEM pipeline stage.
應改為 ID pipeline stage
(b) Assume the percentage of load instruction is 20% in a program
, and half the time the instruction following a load needs
the result of the load instruction.
Then , the performance degradtion due to the data hazard is 1.1
1 + 0.2* (1/2)
Performance = ────── = 1.1
1
performance degradtion due to the data hazard = 1.1 - 1 = 0.1
(e) All of the above are correct.
Ans: a,b,e
台大電機 99
Which of the following statement are true ?
(a) If the data requested by a load instruction has not yet become
availble when it is requested , the load-use data hazard occur.
when its next and dependency instruction is requested
(b) Data hazard may be resolved with bypassing technique which
retrieve the hitting data element from internal buffers
rather than waitting for it to arrive from external memory
hitting 應改為 missing
(c) If the proper instruction cannot execute in proper clock cycle
because the instruction that was fetched is not that is needed
, the data hazard occurs .
control hazard

99(a)load-use是指在load後面的指令所需資源還沒好不是load所需資源還沒好99(c)題目敘述應該是control hazard99(b)不太確定，不過是從pipeline register取得資料不知道題目的internal buffer是指什麼100年b 因為是問degradation，所以要扣掉原本的100(b)應該說重點是due to data hazard

100 答案是abe e選項是選項全對？怎麼怪怪的0.0

不過internal buffer如果是指pipeline register，那b選項不就是正確嗎？紅字那段的原文是課本寫的嗎

100那題是問那些有錯，所以要選e。那年題目選項好幾題都這樣99b hitting要改missing by張凡課本，internal buffer是指pipeline register 應該沒錯，張凡有題中央100的解答有這寫法。