问题 单项选择题 案例分析题

高速缓存Cache与主存间采用全相联地址映像方式,高速缓存的容量为4MB,分为4块,每块1MB,主存容量为256MB。若主存读写时间为30ns,高速缓存的读写时间为3ns,平均读写时间为3.27ns,则该高速缓存的命中率为(1)%。若地址变换表如下所示,则主存地址为8888888H时,高速缓存地址为(2)H。

空白(2)处应选择()

A.488888

B.388888

C.288888

D.188888

答案

参考答案:D

解析:对于高速缓存Cache,设H为其命中率,t为其存取时间,t为主存的访问时间,t为Cache存储器的等效加权平均访问时间,则有t=Ht+(1-H)t。对于本题,则有30×(1-H)+3×H=3.27,可以求得H=0.99,即Cache的命中率为99%。对于第2题,主存地址为8888888H时,转换为二进制地址为1000100010001000100010001000B,其中块号为10001000H,即88H。块内地址为10001000100010001000B,即88888。由地址变换表知Cache对应的块号为1H,所以Cache的地址为188888H。

阅读理解

阅读理解。

     Three women escaped from prison (监狱). They ran for miles until they came upon an old barn (仓房).

They decided to hide (隐藏) in the hayloft (干草棚) and rest. When they climbed up, they found three bags

and decided to hide inside them.

     About an hour later the head of the town and his assistant came into the barn. The head told his assistant

to go up and check out the hayloft. When he was up there, the head asked him what he saw. The assistant

shouted back, "Just three large bags."

     The head told him to find out what was in them, so the assistant kicked the first bag, where one of the

women was hiding. She went, "Wow -Wow", so the assistant told the head that there was a dog in the bag.

     Then he kicked the second bag that the second woman was hiding in. She went, "Meow," so the assistant

told the head that there was a cat in the bag.

     Then he kicked the bag that the third woman was in, and there was no sound at all, so he kicked it again,

and the woman cried, "Potatoes."

1. Three women went into an old barn to ________.

A. hide

B. find the bags

C. run away

2. In the third paragraph the underlined word "went" means ________.

A. 去

B. 叫

C. 走开

3. The assistant kicked the third bag again because he wanted to _________.

A. find some potatoes

B. kick the woman

C. find out what was in it

4. Which of the following is TRUE?

A. The head and his assistant reached the bam before the three women.

B. The head climbed up and checked the hayloft.

C. The assistant thought that there was a cat in die second bag.

5. From the passage we know that ________.

A. the third woman was clever

B. the prison was next to the barn

C. the head would find the women

选择题