问题 单项选择题

假设微处理器的主频为50MHz,两个时钟周期组成一个机器周期,平均三个机器周期完成一条指令,则它的机器周期是 (6) ns,平均运算速度约为 (7) MIPS。

A.2

B.3

C.6

D.8

答案

参考答案:D

解析:试题6~7

[分析]: 计算机主频的周期是指时钟周期,时钟周期表示了SDRAM所能运行的最高频率,更小的时钟周期就意味着更高的工作频率。
CPU周期又称机器周期,是CPU访问一次内存所花的时间,因此用从内存读取一条指令字的最短时间来定义。
题目中告诉我们,两个时钟周期组成一个机器周期,而微处理器的主振频率为 50MHz,即时钟周期=1/50MHz=20ns,由此可以计算出机器周期两倍时钟周期为40ns。
MIPS(每秒百万条指令)是表示机器运算速度的单位,意思是每秒钟所能执行的指令条数。在本题中,由于平均每3个机器周期完成一条指令,而一个机器周期的为40ns,因此,平均执行一条指令需要120ns的时间。也就是说,每秒钟能执行的指令条数为 1/120ns,即8.3×106条指令,也就是8.3MIPS。

单项选择题
单项选择题

It was two years ago today that the hunting ban came into force, supposedly ending centuries of tradition. However, the law has been an unmitigated failure-not that either side is shouting about it.
It was a nightmare vision that struck fear and loathing into the hearts of millions. When the hunting ban became law, it was said, 16, 000 people would lose their jobs, thousands of hounds would be put down, rotting carcasses would litter the countryside, hedgerows would disappear, riders would face on-the-spot fines, law-abiding people from doctors to barristers would be dragged from their horses and carted off to prison, while dog owners would be prosecuted if their mutt caught a rabbit.
These were just some of the claims as desperate countryside campaigners battled to save their sport in the lead-up to the hunting ban, which Labour rammed into law using the Parliament Act on November 18, 2004.
For many, the fears were real. Others exaggerated as they fought an increasingly aggressive anti-hunting lobby which had rejected acres of independent evidence affirming that hunting is the most humane way of killing foxes. In the battle to"fight prejudice, fight the ban", every emotive argument was deployed.
For its part, the anti-hunting brigade extravagantly claimed that the ban would put an end to the rich parading in red jackets. A senior Labour MP, Peter Bradley, admitted in this newspaper that it was, as many suspected, about "class war". He lost his seat shortly afterwards. But people in red coats did not disappear.
In fact, none of the forecasts came true. What did happen was something nobody had predicted: the spectacular revival and growth of hunting with hounds. In short, the hunting ban has been a failure.
Today, on the second anniversary of the ban’s coming into force on February 18, 2005, new figures show that participation in the sport has never been higher. It is so cheerful that two new packs have been formed, something that has not happened for centuries.
They include the seductively named Private Pack, set up by the financier Roddy Fleming in Gloucestershire. It operates on an invitation-only basis, a sort of hunting private members’ club. This can only mean one thing: like it or not, hunting is cool. Young people are taking it up, enticed by the element of rebellion and the mystique of what actually happens as hunts attempt to keep within the law.

By saying "people in red coats did not disappear," the author implied that ______.

A.the upper class won the "war"

B.Bradley deserved his fate

C.the hunting ban did not work

D.the hunting ban was untimely