[理工] [計組]direct mapped cache

[jim055006 (jim)]

問題如下:

Assume the three caches below, each consisting of 16 words. Given the
series of address references as word addresses:2, 3, 4, 16, 18, 4, 2. Please
label each reference as a hit or a miss for the three caches (a), (b) and (c)
below. Assuming that LRU is used for each replacement algorithm and all the
caches are initially empty.

(a)a direct-mapped cache with 16 one-word blocks.
(b)a direct-mapped cache with 4 four-word blocks.
(c)For each of above (a) and (b) caches, how many misses are
   compulsory misses?
(d)For each of above (a) and (b) caches, how many misses are
   conflict misses?

-------------------------------------------------------------------------------
答案如下:


(a) direct-mapped cache with 16 one-word blocks.

address   Block no.   index   tag    H/M
-----------------------------------------------------------
   2          2         2      0      M     compulsory miss
   3          3         3      0      M     compulsory miss
   4          4         4      0      M     compulsory miss
  16         16         0      1      M     compulsory miss
  18         18         2      1      M     compulsory miss
  16         16         0      1      H
   4          4         4      0      H
   2          2         2      0      M     conflict  miss


(b) direct-mapped cache with 4 four-word blocks.

address   Block no.   index   tag    H/M
-----------------------------------------------------------
   2          0         0      0      M     compulsory miss
   3          0         0      0      H
   4          1         1      0      M     compulsory miss
  16          4         0      1      M     compulsory miss
  18          4         0      1      H
  16          4         0      1      H
   4          1         1      0      H
   2          0         0      0      M     conflict miss


紅色閃爍的地方為什麼不是conflict miss?
有勞高手解惑一下...
鋼溫!!

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推 CrazyBoss:張凡說不管cache有沒有data，只要這個binary addr第一次
→ CrazyBoss:進去cache就算了
推 mqazz1:我想你應該要先去看一下定義
→ jim055006:我看了....我一直以為區塊重未被使用過...第一次讀取
→ jim055006:此區塊，必不在cache中
→ jim055006:那個區塊不是只cache block嗎?
推 genius945:block指的應該是要從memory抓來的block
→ genius945:我懂原PO的意思,想成是空的cache區塊就是compulsory
→ jim055006:對!!我是這個意思....G大真懂我
→ genius945:但miss的本意是找不到所要的資料,重點要放在"要找的"
→ jim055006:我知道我想錯了...如果想成M.M block就都說得通了
→ jim055006:謝謝大家....我弄懂了....就甘心!!
推 da0910cc:課本有個地方,有說tag,index,direct,2-way等等的定義
→ da0910cc:我忘了在哪了,那邊看懂應該就沒問題了!
→ sneak: 謝謝大家....我弄懂 https://daxiv.com