After-school exercise 8 (I/O system)

After-school exercise 8 (I/O system)

1. Multiple choice questions (10 questions in total, 100 points)

1. (Multiple choice)
I/O addressing methods can usually be divided into unified addressing and non-uniform addressing, ( )

• A. Unified addressing is to regard the I/O address as a part of the memory address, and use special I/O instructions to access the device
• B. Non-uniform addressing means that the I/O address and the memory address are separated, so there must be a special I/O instruction for I/O access
• C. Unified addressing means that the I/O address and the memory address are separated, so the CPU access to the device can be realized by using the memory access instruction
• D. Not uniform addressing is to treat the I/O address as part of the memory address, but there must be a special I/O instruction for I/O access

My answer:  B Correct answer:  B

10 points

2. (Multiple choice)
Regarding the DMA method, which of the following descriptions is correct ( )

• A. Since the DMA method can be used for information transfer of high-speed peripheral devices, it can also replace the interrupt method
• B. The DMA method cannot replace the interrupt method
• C. DMA method is a pure software method
• D. DMA mode is an operation mode that has nothing to do with main memory during operation

My answer:  B Correct answer:  B

10 points

3. (Multiple choice) Among
the following devices, ( ) has input and output functions

• A. Disk drive
• B. Keyboard
• C. Traditional monitor (without touch function)
• D. Printer

My answer:  ACorrect answer:  A

10 points

4. (Multiple choice)
Among the following options, the information transmitted on the data line of the I/O bus includes ( )

I. Command word in the I/O interface   

II. STATUS WORD IN I/O INTERFACE   

III. Interrupt Type Number

• A. 仅 I sum II
• B. I and III only
• C. II and III only
• D. I II 、 III

My answer:  D Correct answer:  D

10 points

5. (Multiple choice question)
The letter and character encoding commonly used in minicomputers and microcomputers is ( )

• A. BCD code
• B. Hexadecimal code
• C. ASCII code
• D. Two's complement

My answer:  C Correct answer:  C

10 points

6. (Multiple choice)
When using DMA to transfer data, it takes ( ) time for each data transfer

• A. One instruction cycle
• B. One Machine Cycle
• C. One storage cycle
• D. One clock cycle

My answer:  C Correct answer:  C

10 points

7. (Multiple choice)
Assume that the display memory of a computer is implemented by a DRAM chip. If the display resolution is 1600×1200, the color depth is 24 bits, the frame frequency is 85Hz, and 50% of the total display bandwidth is used to refresh the screen , the total required memory bandwidth is at least about ( )

• A. 245 Mb / S
• B. 979 Mb / S
• C. 1958 Mb / S
• D. 7834 Mb / S

My answer:  D Correct answer:  D

10 points

Answer analysis:

Note the difference between Mb/S and MB/S

8. (Multiple choice)
Assume that the running time of benchmark program A on a computer is 100 seconds, of which 90 seconds are CPU time and the rest are I/O time. If the CPU speed is increased by 50% and the I/O speed is unchanged, the time it takes to run program A is ( )

• A. 55 seconds
• B. 60 seconds
• C. 65 seconds
• D. 70 seconds

My answer:  D Correct answer:  D

10 points

Answer analysis:

CPU time 90 seconds, I/O time 10 seconds,

The CPU speed is increased by 50%, that is, the new time t*(1+50%)=90, and the calculation t=60 seconds

I/O time has not been mentioned, still 10 seconds

Overall results

9. (Multiple choice)
A computer with a main frequency of 50MHz uses a timed query method to control the I/O of device A. The number of clock cycles used by the query program to run once is at least 500. During the operation of device A, in order to ensure that data is not lost, every It needs to be queried at least 200 times per second, then the percentage of the I/O time used by the CPU for device A in the entire CPU time is at least ( )

• A. 0.02 ％
• B. 0.05 ％
• C. 0.20 ％
• D. 0.50 ％

My answer:  C Correct answer:  C

10 points

Answer analysis:

The main frequency is 50MHz, then a clock is 20ns,

If the query program runs for 500 cycles, then a query is 20ns*500=10us

Query at least 200 times per second, then the query time is 10us*200=2ms

The above calculation unit period is second, then the proportion is 2ms/1=0.002

10. (Multiple choice)
When the host and the device transmit data, use ( ), the host and the device work serially

• A. Program query method
• B. Interrupt method
• C. DMA method
• D. All three of the above are acceptable

My answer:  ACorrect answer:  A