设时钟频率为SMHz，该指令的机器码为4个字节，存放在1000H:2000H开始的代码段中。8086 CPU执行MOV[2003H]，AX指令语句后，从取指到执行指令最少需要多少时间
参考答案：该条指令的机器码为4个字节存放在1000H:2001H开始的4个单元中，则取指令需2个总线周期，第一次取出1000H:2000H与1000H:2001H 2个单元中的16位代码；第二次取出1000H:2002H与1000H:2003H二个单元中的16位代码；接着为执行指令，将AX中16位数传送到DS:2001H与DS:2002H两个存储单元中，因是奇地址字，需2个总线周期才能完成。这样，从取指到执行共需4个总线周期。在无等待周期的情况下，从取指到执行共需：
4×4×1/5M=3.2μs(一个总线周期在无等待周期的情况下由4个时钟周期T组成)。
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| Some myths (神话) are stories told since ancient times to explain the causes for natural happenings. The Greek myth that explains why there are changes of 1 is about Demerter, the goddess of the harvest. She had a daughter, Persephone, whom she loved very much. Hades, god of the underworld, fell in love with Persephone, and he asked Zeus, the 2 of the gods, to give Persephone to him as his 3 . Zeus did not want either to disappoint Hades or to upset Demeter, so he said he would not agree to the marriage, but neither would he 4 it. Hades, therefore, decided to take the girl without 5 . When Persephone was picking flowers in the garden, he seized her and took her to the underworld. When Demeter 6 what happened to Persephone, she became so 7 that she caused all plants to 8 . People were in 9 of starving (挨饿). But Demeter was determined not to let crops grow 10 her daughter, Persephone, was returned to her. 11 , still not wanting to disappoint Hades, decided upon a condition for Persephone's 12 . She could go back to her mother if she had not 13 anything while she was in the underworld. Demeter 14 it because she did not know that Persephone had eaten several Pomegranate (石榴) seeds in the underworld. When Zeus 15 this, he agreed that Persephone could spend part of the year with her 16 , but he added that since she had eaten the seeds, she must spend part of the year in the underworld. And so it 17 that when Persephone is in the underworld, Demeter is sad and therefore 18 not let the crops grow. That is 19 we have winter when plants do not grow. When Persephone returns, Demeter is 20 , it is spring, and plants begin to grow again. | ||||
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