1. The bus of a computer is like the highway of a computer , Can you name the main functions and categories of the bus ?
function , Connect the parts of a computer together , It is usually used to connect CPU, Memory and IO equipment .
classification ： On chip bus , system bus ; System bus can be divided into data bus , Address bus , Control bus .
2. What is the bus standard , Why bus standards are needed , What are the common bus standards now ?
The bus standard is used to standardize the system and each module , A standard for interconnection between modules .
With the bus standard , Different manufacturers can produce equipment according to the same standards and specifications , Achieve the purpose of interconnection .
Common standards ：ISA,PCI,USB,PCIe.
3. It's often said "IO equipment ', "I","O" What are their abbreviations ?
IO The devices are Input and Output Abbreviation for
4. What kinds of common input devices can be divided into ?
Character input ： keyboard .
Image input ： mouse , Digital plate , Scanner .
5. What kinds of common output devices can be classified ?
Classification of output devices ： screen , printer .
6. Common computer peripherals （ monitor , keyboard , mouse , printer ）, What kind of equipment do they belong to ?
output , input , input , output .
7. I / O interface — What kind of work should be done , Can divide the line of interface into what line ?
Connect external devices with CPU Connect , Information exchange .
Line classification ： data line , State line , Command line , Address line .
8. DMA What is the full name of ?
Direct memory access .
9. Program interruption and DMA comparison , What are the advantages and disadvantages ?
advantage ： Program interrupt is easy to implement ,DMA High equipment cost .
inferiority ： Frequent interruptions are required CPU, reduce CPU Processing efficiency of .
10. Can you clearly describe the hierarchy of computer memory ? What is the purpose of memory hierarchy ?
Memory hierarchy ： cache , Main memory , Auxiliary deposit .
cache - Main memory to solve the problem of insufficient main memory speed , Main memory - Secondary storage is to solve the problem of insufficient main memory capacity .
11. What is the principle of locality , How does locality affect the design of computer storage system ?
Principle of locality ： Time locality ： A block of memory used may be reused in the near future ; Spatial locality ： Memory in the vicinity of a used memory block may be used .
influence ： Each layer of the computer memory hierarchy caches the next layer （ It's a little slower ） Part of the data .
12. What are the characteristics of each level of computer storage system ?
The faster the speed , The higher the cost ; leave CPU The further away , The slower the speed .
13. Computer auxiliary memory generally refers to computer hard disk , Do you know the physical structure of computer disks ?
understand , A disk usually has more than one disk , There is a magnetic head on each disk , The heads move synchronously . Each disk is divided into tracks （ cylinder ）, a sector . Disk read time = Seeking truth + rotate + transmission .
14. What are the disk scheduling algorithms ? What are their characteristics ?
Disk scheduling algorithm ：
First come, first served algorithm FIFO： Schedule according to the order of process requests to access the disk .
Shortest seek time SSTF： In request queue , Find the most recent service in progress .
Elevator algorithm （ Scanning algorithm ）SCAN： Swing scanning algorithm , The direction of each movement is single , Only in or out .
Cyclic scanning algorithm C-SCAN： One way movement of magnetic head , After visiting the end of one end , Go back to the other end immediately .
LOOK and C-LOOK
15. The main memory of a computer generally refers to the computer memory , What are the characteristics of memory ?
Memory is CPU Direct addressable storage unit , Fast access , Generally used RAM storage . Data loss in case of power failure .
16. Please explain the concept ： Main memory , Auxiliary deposit ,Cache,RAM,ROM?
Main memory ： Direct to CPU Devices that provide storage , high speed , Power failure cannot be saved .
Auxiliary deposit ： Generally refers to external memory , Like hard disk , CD and so on , This kind of memory can still store data after power failure .
Cache： cache , Located in CPU Between and memory .
RAM： Random access memory , Data loss due to power failure .
ROM： read-only memory , Cannot be modified or deleted after storage .
17. What is a word ? What are chunks ?
word ： A binary unit in a storage unit , Word length is the number of digits in a word .
Word block ： A set of words stored in a contiguous storage cell and treated as a unit .
18. The cache of a computer generally refers to Cache, Cache What hardware devices are generally located on the computer ?
On the motherboard or CPU upper .
19. — What indicators are used to evaluate main memory － Cache performance ?
hit rate , Access efficiency .
20. How is the hit rate defined ?
The number of times the cache was accessed / Total visits .
21. How is access efficiency defined ?
Time to access cache / Total visit time .
22. hypothesis CPU Execute a certain program, total visits Cache Hit 4800 second , Access to main memory 200 second , Known Cache The access cycle of 30ns, The access cycle of main memory is 150ns,
seek Cache- Average access time and efficiency of main memory system , How much performance has been improved ?
hit rate = 4800 / 5000 = 0.96
average access time = 30ns * 0.96 + 150ns * 0.04 = 34.8ns
Access efficiency = 30/34.8 = 0.8621 = 86%
Improved (150-34.8）/150 * 100% = 76.8%
23. Predicate description LFU ,LRU ,FIFO The process of cache replacement algorithm .
LFU： Least use algorithm , Eliminate the most frequently used memory block .
LRU： Recent algorithms , Eliminate pages that have not been used recently .
FIFO： FIFO algorithm , The first memory block entered is replaced by the first one .
24. The instruction of computer is generally composed of operation code and address code , Then computer instructions can be classified into several types ?
Instruction type ： Shift operation instruction , Data transfer instruction , Control instruction and arithmetic logic operation instruction .
25. What are the ways to address computer instruction data ?
Immediate addressing , Direct addressing , Indirect addressing .
26. What are the main components of a computer's arithmetic unit ? What about the controller ?
Composition of arithmetic unit ：ALU, Status register , accumulator （ Data buffer ）, General register .
Composition of controller ： Program counter PC, control unit CU, Instruction register IR.
27. Please briefly describe the execution process of computer instructions .
It is mainly divided into taking instructions , Analysis instruction , Execute instruction .
from PC Get instruction address to MAR in , Control unit according to MAR Address in memory to get instructions , The retrieved instructions are placed in the MDR in ,MDR Give the instructions to the decoder ID Analysis , Then execute the instruction .