《计算机组成原理》第三章课后题参考答案.doc

第三章课后习题参考答案1 有一个具有20位地址和32位字长的存储器，问：（1） 该存储器能存储多少个字节的信息？（2） 如果存储器由512K×8位SRAM芯片组成，需要多少芯片？（3） 需要多少位地址作芯片选择？解：（1） 220= 1M， 该存储器能存储的信息为：1M×32/8=4MB （2）（1024K/512K）×（32/8）= 8（片） （3） 需要1位地址作为芯片选择。3 用16K×8位的DRAM芯片组成64K×32位存储器，要求：(1) 画出该存储器的组成逻辑框图。(2) 设DRAM芯片存储体结构为128行，每行为128×8个存储元。如单元刷新间隔不超过2ms，存储器读/写周期为0.5S, CPU在1S内至少要访问一次。试问采用哪种刷新方式比较合理？两次刷新的最大时间间隔是多少？对全部存储单元刷新一遍所需的实际刷新时间是多少？解：（1）组成64K×32位存储器需存储芯片数为N=（64K/16K）×（32位/8位）=16（片）每4片组成16K×32位的存储区，有A13-A0作为片内地址，用A15 A14经2：4译码器产生片选信号 ，逻辑框图如下所示：（2）根据已知条件，CPU在1us内至少访存一次，而整个存储器的平均读/写周期为0.5us，如果采用集中刷新，有64us的死时间，肯定不行；所以采用分散式刷新方式：设16K×8位存储芯片的阵列结构为128行×128列，按行刷新，刷新周期T=2ms，则分散式刷新的间隔时间为：t=2ms/128=15.6(ms) 取存储周期的整数倍15.5ms(0.5的整数倍)则两次刷新的最大时间间隔发生的示意图如下可见，两次刷新的最大时间间隔为tMAX tMAX15.5×20.530.5 (S)对全部存储单元刷新一遍所需时间为t R t R0.5×128=64 (S)4有一个1024K×32位的存储器，由128K×8位DRAM芯片构成。问：(1) 总共需要多少DRAM芯片？(2) 设计此存储体组成框图。(3) 设DRAM芯片存储体结构为512行，每行为256×8个存储元。采用分散式刷新方式，如单元刷新间隔不超过8ms，则刷新信号周期是多少？解：（1）总共需要DRAM芯片数为：N=（1024K/128K）×（32位/8位）=32（片）（2）此存储体组成框图 (3)如果选择一个行地址进行刷新，刷新地址为A0-A8，因此这一行上的256×8个存储元同时进行刷新，即在8ms内进行512个周期。在8ms中进行512次刷新操作，按分散刷新方式8ms/512 = 15.5us刷新一次。5. 要求用256K×16位SRAM芯片设计1024K×32位的存储器。SRAM芯片有两个控制端：当有效时，该片选中。当=1时执行读操作，当=0时执行写操作。解：所设计的存储器单元数为1M，字长为32，故地址长度为20位（A19A0），所用芯片存储单元数为256K，字长为16位，故占用的地址长度为18位（A17A0）。由此可用位并联方式与地址串联方式相结合的方法组成组成整个存储器，共8片RAM芯片，并使用一片2：4译码器。其存储器结构如图所示。7某机器中，已知配有一个地址空间为0000H-3FFFH的ROM区域。现在再用一个RAM芯片(8K×8)形成40K×16位的RAM区域，起始地址为6000H,假定RAM芯片有和信号控制端。CPU的地址总线为A15-A0，数据总线为D15-D0，控制信号为R/(读/写)， (访存)，要求：（1） 画出地址译码方案。（2） 将ROM与RAM同CPU连接。解：（1）依题意，主存地址空间分布如下图所示，ROM区16K×16位；10片的8K×8位RAM片组成40K×16位的RAM区。ROM需14位片内地址，而RAM需13位片内地址，故可用A15-A13三位高地址经译码产生片选信号,方案如下:（2）ROM和RAM与CPU连接图：8 存储器容量为64M，字长64位，模块数m = 8，分别用顺序方式和交叉方式进行组织。存储周期T = 100ns,数据总线宽度为64位，总线周期= 50ns。若连续读出8个字，问顺序存储器和交叉存储器的带宽各是多少？解：信息总量：q=64位×8=512位 顺序存储器和交叉存储器读出8个字的时间分别是：t2=mT=8×100ns=8×10(s)t1=T+ (7-1)* =100+7×50= 4.5×10(s)顺序存储器带宽是：W2= q/t2=512÷（8×10）=64×10（位/S）交叉存储器带宽是：W1=q/t1=512÷（4.5×10）=113.8×10（位/S）9 CPU执行一段程序时, cache完成存取的次数为2420次，主存完成存取的次数为80次，已知cache存储周期为40ns，主存存储周期为240ns，求cache/主存系统的效率和平均访问时间。解：先求命中率hh=Nc/(Nc +Nm )2420÷(242080)0.968则平均访问时间为tatah×tc +(1-h) ×tm =0.968×40(1-0.968) ×24046.4(ns)cache/主存系统的效率为eetc/ta=40/46.486.210已知cache存储周期40ns，主存存储周期200ns，cache/主存系统平均访问时间为50ns，求cache的命中率是多少？解：根据tah×tc +(1-h) ×tm得h=(tm-ta)/ (tm-tc)=(200-50)/(200-40)=0.9375以下是大学体验英语综合教程2(第三版)课后翻译答案Unit11. 任何年满18岁的人都有资格投票。(be eligible to, vote)Answer:Anyone over the age of 18 is eligible to vote. 2. 每学期开学前，这些奖学金的申请表格就会由学校发给每一个学生。(apply for, scholarship)Answer:A form to apply for these scholarships is sent by the university to every student before the start of every semester. 3. 遵照医生的建议，我决定戒烟。(on the advice of)Answer:On the advice of my doctor, I decided to give up smoking. 4. 公园位于县城的正中央。(be located in)Answer:The park is located right in the center of town. 5. 这所大学提供了我们所需的所有材料和设备。(facilities) Answer:The university provides all the materials and facilities we desire.1. 他们花了多年的时间寻找内心的平静，但是收效甚微。(search for)Answer:They spent many years searching for peace of mind, but with little success. 2. 这种新药的成功研制已经使许多疾病的治疗发生了根本性的变革。(revolutionize)Answer:The successful development of the new drug has revolutionized the treatment of many diseases. 3. 由于这个国家的经济不景气，这家公司濒于破产。(on the edge of)Answer:The company is on the edge of bankruptcy due to the economic depression in the country. 4. 大学毕业后他成为了一名护士。他认为护士这一职业可能很有发展前途。(rewarding)Answer:He became a nurse after college. He thought nursing could be a very rewarding career. 5. 他像往常一样在文件上签了名。(just as) Answer:He signed his name on the paper just as he has always done it.Unit21. 警察们正忙着填写关于这场事故的各种表格。(fill out)Answer:The policemen are busy fi lling out forms about the accident. 2. 我想在还车之前把油箱加满。(fill up, fuel tank)Answer:I want to fi ll up the fuel tank before returning the car. 3. 如果你要投诉，最好遵循正确的程序。(follow the procedure)Answer:If you want to make a complaint, youd better follow the correct procedure. 4. 要不是约翰帮忙，我们绝不会这么快就完成实验。(without)Answer:We couldnt have fi nished the experiment so soon without Johns help. 5. 暴风雨之后，岸边的人们焦急地搜索湖面以期发现小船的踪迹。(scan for)Answer:After the storm, the people on the shore anxiously scanned the lake for any sign of the boat.1. 这个国家不大，但是在国际事务中它却发挥着重要作用。(play a role)Answer:This country is not big, but it plays an important role in international affairs. 2. 正是在我叔叔的帮助下，我得以克服困难，按时完成了任务。(it is . that)Answer:It was with the help of my uncle that I overcame the difficulty and completed the assignment in time. 3. 毕业时他决定留在北京，而他最好的朋友却选择了去西藏。(while)Answer:While he decided to stay in Beijing upon graduation, his best friend chose to go to Tibet. 4. 在这次校园英语演讲比赛中，我们班的玛丽获得了第三名。(come in)Answer:In this Campus English Speaking Contest, Mary from our class came in third. 5. 你应该知道学习弹钢琴需要有时间，有金钱，还要有毅力。(as well as) Answer:You should know that it takes time, money as well as perseverance to learn to play the piano.Unit31. 我发现量入为出地过日子越来越难了。(increasingly) Answer:I find it increasingly difficult to live within my income.2. 现代政治家们都试图以电视讲话来影响普通百姓。(reach out) Answer:Modern politicians try to reach out to ordinary people in their TV speeches.3. 应该帮助学生对人生采取积极的态度。(adopt) Answer:Pupils should be helped to adopt a positive attitude to life.4. 希望全班同学参加这些讨论。(participate in) Answer:Everyone in the class is expected to participate in these discussions.5. 如果你犯了罪就必须受到惩罚。(crime) Answer:If you commit a crime you must expect to be punished.1.儿子的死让老妇人变得麻木痴呆了。(numb)Answer:The old woman was numbed by her sons death.2.身处所有这些烦恼之中，他依然能保持乐观。(in the midst)Answer:In the midst of all troubles, he managed to remain cheerful.3. 虽有困难，他们还是设法坚持试验下去。(carry on) Answer:They managed to carry on their experiments in spite of the difficulties.4.我们必须淘汰不合格的申请人。(weed out) Answer:We have to weed out unqualified applicants.5. 医生要他减少抽烟。(cut down on) Answer:The doctor told him to cut down on smoking.Unit41.她在公共汽车站一直等到末班车进站。(come in)Answer:She waited at the bus stop until the last bus came in.2.如果我们能帮得上忙，尽管和我们联系。(contact)Answer:If there is any way we can be of assistance, please do not hesitate to contact us.3 .他需要多少船务人员才能使他的游艇航行？(crew, yacht)Answer:How many crew does he need to sail his yacht?4 .虽然她的新书没有上一本好，但是我还是喜欢它。(not quite as)Answer:I enjoyed her new book though its not quite as good as her last one.5 .我从未遇到过如此善良的人。(never before)Answer:Never before have I met such a kind person.1.公共汽车放慢速度并停下，让那位乘客上车。(slow down)Answer:The bus slowed down and stopped to allow the passenger to get on board.2.许多车子都驶过去了，可是没有一辆愿意让我们搭便车。(roll by)Answer:Many vehicles rolled by, but no one offered us a ride.3 .请勿践踏草地。(get off)Answer:Please get off the grass.4.他按妻子的吩咐，一下班就去了市场。(make ones way)Answer:He made his way to the marketplace right after work, as his wife had asked him to do.5 .值得庆幸的是，史蒂夫 (Steve) 从自行车上摔下来时没有摔断骨头。(luckily)Answer:Luckily, Steve didnt break any bones when he fell off his bike.Unit51. 我们得把感情放在一边，从专业的角度来对待这件事。(from a professional standpoint)Answer:We have to put aside our emotions and take it from a professional standpoint.2. 这部戏非常精彩，我很快就沉浸于激动人心的剧情之中。(lose oneself in)Answer:The play was so wonderful that I soon lost myself in the excitement of it.3 .她没有什么爱好除非你把看电视也算是一种爱好。(unless)Answer:She hasnt got any hobbies unless you call watching TV a hobby.4. 他说他是直接从市长本人那里得到这个信息的。(first-hand)Answer:He said that he had got the information first-hand from the Mayor himself.5 .既然你不能回答这个问题，我们最好问问别人。(since)Answer:Since you cant answer the question, perhaps wed better ask someone else.1. 由于公共汽车司机突然刹车，旅客们都不由自主地向前摔倒。(brake, pitch forward)Answer:All the passengers pitched forward because the bus driver braked sharply.2. 这个协议将冲破对自由贸易设置的障碍。(break through, obstacle)Answer:This agreement will break through the obstacles to free trade.3 .我刚放下叫出租车的电话，车就来了。(soon after)Answer:The taxi arrived soon after I rang for it.4. 在过去，不管我什么时候到家，我父母总会等我。(no matter)Answer:My parents always waited up for me no matter what time I got home.5 .由于没有一方愿意让步，两个公司之间的对话完全破裂了。(break down)Answer:Talks between the two companies completely broke down, because neither of them wanted to give in.Unit61. 那件工作很难做，不过我想试试看。(have a shot) Answer:Its a difficult job, but Id like to have a shot.2. 这是一本关于商务实践而非理论的书。(as opposed to)Answer:This is a book about business practice as opposed to theory.3. 社会活动从未耽误她的学习。(in the way) Answer:Social activities never get in the way of her studies.4. 直到1911年人们才发现第一种维生素。(It is not until . that) Answer:It was not until 1911 that the first of the vitamins was identified.5. 尽管年事已高，爷爷每天还帮忙做家务。(despite)Answer:Despite advanced years, Grandpa helps do housework every day.1. 我们的婚姻很幸福，但我们也曾经历过许多坎坷。(ups and downs)Answer:Our marriage is happy but weve had many ups and downs. 2. 许多外语教师常常在课堂上自顾自地讲得太多。(be inclined to)Answer:Many teachers of foreign languages are inclined to talk too much themselves in class. 3. 那位著名演员每天早晨锻炼一小时以保持健康。(work out)Answer:The famous actor keeps fit by working out for an hour every morning. 4. 与他促膝长谈之后，她的怀疑消失了。(melt away)Answer:After a long heart-to-heart talk with him, her suspicion melted away. 5. 目前我们没有职位空缺，但我们肯定会记住您的申请。(keep in mind)Answer:We have no vacancies now, but well certainly keep your application in mind.Unit71. 他并不后悔说过的话，只是觉得他完全可以不用这种方式表达。(could have done)Answer:He did not regret what he had said but felt that he could have expressed it differently.2. 我们最好等到12月14日。那时大卫已考完试，就能和我们一起去度假了。(will have done)Answer:Wed better wait till 14 December. David will have had his exam by then, so hell be able to go on holiday with us.3. 他正在做一个新项目，年底前必须完成。(work on)Answer:Hes working on a new project which has to be finished by the end of the year.4. 他们让我们使用他们的实验室，作为回报，我们则让他们分享研究成果。(in return)Answer:They are letting us use their lab, and in return, we are sharing with them the results of our research.5. 诸如打电话、听电话一类的事情占用了这位秘书的大部分时间。(take up)Answer:Such things as making and answering telephone calls take up most of the secretarys time.1. 他们把房子卖了后就到加拿大和女儿住在一起。(go off) Answer:They sold their house and went off to live in Canada with their daughter.2. 你下星期这个时候会在干什么？还是像平常一样干活。(will be doing) Answer:What will you be doing this time next week?Ill be working as usual.3. 他既聪明又勤奋，不久就接管了杂志的编辑工作。(editing; before long)Answer:He was intelligent and hard-working and before long he took over the editing of the magazine.4. 你话还没说完别人就挂断电话，难道你不恼火吗？(hang up)Answer:Dont you hate it when someone hangs up on you before you finish speaking?5. 让他们感到惊恐的是，他们的房顶着火了。(to ones horror)Answer:To their horror, the roof of their house caught fire.