问题 单项选择题

以下关于Cache的叙述中,正确的是______。

A.在容量确定的情况下,替换算法的时间复杂度是影响Cache命中率的关键因素

B.Cache的设计思想是在合理成本下提高命中率

C.Cache的设计目标是容量尽可能与主存容量相等

D.CPU中的Cache容量应大于CPU之外的Cache容量

答案

参考答案:B

解析:
本题考查高速缓存基础知识。
Cache是一个高速小容量的临时存储器,可以用高速的静态存储器(SRAM) 芯片实现,可以集成到CPU芯片内部,或者设置在CPU与内存之间,用于存储CPU最经常访问的指令或者操作数据。Cache的出现是基于两种因素:首先是由于CPU的速度和性能提高很快而主存速度较低且价格高,其次是程序执行的局部性特点。因此,才将速度比较快而容量有限的SRAM构成Cache,目的在于尽可能发挥CPU的高速度。很显然,要尽可能发挥CPU的高速度,就必须用硬件实现其全部功能。

阅读理解

I looked at my beautiful Christmas tree and sighed. It was time. The New Year was a week old and my tree still stood in the corner of our room with its collection of memories proudly displayed in a shower of colorful lights. I’d procrastinated(拖延,耽搁)long enough.

I got up, went to the garage and dragged all the boxes into the room. The garland(花环)was the first to come down. The tree looked naked(光秃秃的)already. I took the large ornament(装饰物)off next. They made a large pile on our bed. An hour later, our bed was covered with Christmas memories. Each pile contained an ornament along with its matching brothers and sisters from sets purchased many years ago.

I prepared the boxes and carefully placed ornaments in their protective packaging, pausing every few minutes to admire a favorite. “Hey, little Santa!” I held the Santa from my childhood. “Thanks for being my friend for almost fifty years.” He was a little ragged but still gives me a flood of wonderful memories. “Until next year, my dear friend.”

There was a collection of handmade ones. My children made in the their first years of school, more than twenty years ago. Made by tiny hands, they are far from perfect in design, but every year they go on my memory tree-memories of young giggles(咯咯地笑)on Christmas morning and a smiling face when they handed them to me when I came home from work. “Look what we made, Daddy!”

“Oh! It is beautiful. Let’s find a special spot on the tree for it.” Every year since, they are displayed.

A few hours after I started, the filled boxes were back in the garage, the room was vacuumed(用吸尘器清扫)and I sat staring at a barren(空荡荡的)corner. The room seemed so empty. It took me two days of work to assemble(收集)and decorate my tree, but only a few hours to take it apart.

My tree is like a good marriage or a great friendship. Like the tree, they take a long time to assemble and decorate with memories, but can be torn down quickly.

Every year I have to put my tree away, but not my marriage or friendships. I take great care of those. They get to glow in the corner of my life for as long as I live. I get to analyze my tree and find memories for a few weeks every year. I can do the same with the loves in my life every day. Take great care of your friendships and your marriage. Once they come down, they aren’t as easy to put back together as a Christmas tree. Stand them in that special spot in the corner of your heart and admire their glow.

小题1:In the author’s eyes, the Christmas tree      .

A.is a collection of childhood memories

B.is a symbol of long-lasting relations

C.takes too much time to decorate

D.is full of out-of-date ornaments小题2:To the author, a Christmas tree is similar to a good marriage in that      .

A.both take time to build but fall apart easily

B.both remind him of bittersweet memories

C.both need to be admired for some time

D.both get less attractive over the years小题3:What is the main theme of the article?

A.We’d better put away Christmas decorations and recycle them each year.

B.Friendships and marriages should be valued and managed carefully.

C.Memories with friends and family should be cherished and relived.

D.We should decorate Christmas trees with personal stuff and recycle.

单项选择题