[理工] [記組]-CPI

看板Grad-ProbAsk作者 (孤獨的風)時間14年前 (2010/03/14 21:21), 編輯推噓4(405)
留言9則, 3人參與, 最新討論串1/1
Consider three different processors P1,P2,P3 excuting the same instruction set with the clock rates and CPIs given in the following table. Processor Clock rate CPI P1 2 GHz 1.5 P2 1.5 GHz 1.0 P3 3 GHz 2.5 Q1.If the processors each excute a program in 10 seconds,find the number of cycles and the number of instructions. _____________________________________________________________________________ 我只知道 P1:1.5=C/I,但兩個未知數根本解不出來 Q2.We are trying to reduce the time by 30% but this leads to an increase of 20% in the CPI.What clock rate should we have to get this time reduction? ______________________________________________________________________________ 題目我就有點看不懂了reduce the time by 30%是指說假設我現在要花10秒,那我就必須變 成7秒,還是3秒? 另一個困擾,對我而言 0.7=(I/Program)*0.8*(seconds/cycles) 有未知數不知來自哪? -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 210.66.168.18

03/14 21:39, , 1F
Q1先求出IC 然後IC*CPI 就是# of Cycles 應該是這樣吧
03/14 21:39, 1F

03/14 21:48, , 2F
減少30% 故是 exe. time =7s CPInew=1.2*CPIoriginal
03/14 21:48, 2F

03/14 21:49, , 3F
但是IC不知道怎麼算,我知道的就是CPI=clock cycles/IC
03/14 21:49, 3F

03/14 21:52, , 4F
exe. time = (IC*CPI)/clock rate
03/14 21:52, 4F

03/14 21:52, , 5F
exe.time , CPI,Clock rate 都有了
03/14 21:52, 5F

03/15 01:23, , 6F
IC * CPI * cycle time = 10sec
03/15 01:23, 6F

03/15 01:24, , 7F
cycle time用clock rate倒數求 CPI給你了 IC就出來了
03/15 01:24, 7F

03/15 01:25, , 8F
第二題用同樣的式子 時間改7sec CPI變1.2倍
03/15 01:25, 8F

03/15 01:25, , 9F
IC第一題有算出來 所以未知數變成Clock rate
03/15 01:25, 9F
文章代碼(AID): #1BdEBIMm (Grad-ProbAsk)