Short Question And Answer Microprocessor Set-4

1. Define EXTRN directive in in 8086 assembly language?
The EXTRN directive is used to inform the assembler that the names or labels following the directive are in some other assembly module.

2. What is the use of TEST instruction in 8086?
Test instruction is the same as the AND instruction except that ite does not put the result anywhere. Like the CMP instruction , it is used only to set the flags.

3. Define LAHF and SAHF instructions in 8086.
LAHF : Load the 8085 equivalent flags into the AH register.
SAHF: Store the AH register into the low order byte of the flag register.

4. While handling the interrupt instructions in 8086. What are the internal operations
may be carried out by the stack?
(i)SP =SP-2 , stack Push flag reg. Contents, IF =0 , TF =0
(ii) SP=SP-2, Stack CS Reg. Contents, Address of Interrupt pointer = Interrupt type * 4 , CS Register Contents Second word of Interrupt pointer
(iii) SP=SP-2, StackIP, IPFirst word of Interrupt pointer

5. Write an ALP program in 8086 to add two 16 bit numbers.
MOV AX,1236H
MOV BX,8765H

6. Write about EVEN directive in 8086 ALP.
It forces the address of the next byte to be even. 8086 words can be accessed in less time if they begin at even address.

7. Write about the following instruction :
Call WORD PTR [BX] Offset of the first instruction of procedure is in two memory addresses in DS. It replaces the contents of IP with contents of word memory locations in DS pointed to by BX.

8. Write an ALP program in 8086 to subtract numbers.
MOV AX,1236H
MOV BX,8765H

9.Define Multiprocessor systems.
If a microprocessor system contains two or more components that can execute instructions independently, then the system is called multiprocessor system.

10.List the advantages of multiprocessor systems.
The multiprocessor system has the following advantages:

  • Improves cost/performance ratio of the system.
  • Several processors may be combined to fit the needs of an application while avoiding the expense of the unneeded capabilities of a centralized system. Yet this system provides room for expansion.
  • Tasks are divided among the modules. If failure occurs, it is easier and cheaper to find and replace the malfunctioning processor than replacing the failing part of complex processor.

11.Write a short notes on closely coupled multiprocessor configuration.
In the closely coupled system, the processors or supporting processors share clock generator, bus control logic, entire memory and I/O subsystem. Such systems can communicate through a shared main memory. Hence the rate at
which data can communicate from one processor to the other is on the order of the bandwidth of the memory.

12.Write a short notes on loosely coupled multiprocessor configuration.
In the loosely coupled systems, each processor has a set of input-output devices and a large local memory where it accesses most of the instructions and data. The processor, its local memory and input-output interfaces are together
called computer module. Processes, which execute on different computer modules, communicate by exchanging messages through a Message Transfer System. The coupling in such a system is very loose. Hence, such systems are
also referred to as distributed systems.

13.What are the advantages of a loosely coupled configuration in a
multiprocessor system?

  • Each processor may have a local bus to access local memory or I/O devices so that a greater degree of parallel processing can be achieved.
  • More flexible.
  • Better system throughput by having more than one processor.
  • If any fault occurs in a module, that faulty module can be detected and replaced. So the breakdown of the entire system is avoidable.

14.What are the several factors that affect the characteristics and performance of a bus?
The factors are:

  • Number of active devices on the bus
  • The bus-arbitration algorithm
  • Centralization or distribution of control
  • Data width
  • Synchronization of data transmission and
  • Error detection

15.Name the three bus allocation schemes used in loosely coupled multiprocessor system.
1. Daisy Chaining
2. Polling method
3. Independent request

16.What are the three basic multiprocessor configurations that the 8086 can support?
1. Coprocessor configuration
2. Closely Coupled Configuration
3. Loosely coupled Configuration

17.What are the three types of contention?
1. Memory contention
2. Communication contention
3. Hot spot contention

18.What are the techniques available for reducing contention?
1. Local Memories
2. Better Interconnection network
3. Cache memory
4. Memory Allocation

19.Explain the need for 8087.
The numeric processor 8087 is a coprocessor, which has been specially designed to work under the control of the processor 8086 and to support additional numeric processing capabilities.

20.Explain the features of 8087.

  • It can operate on data of the integer, decimal, and real types, with lengths ranging from 2 to 10 bytes.
  • Its instruction set not only includes various forms of addition and subtraction, but also provides many useful functions such as square root, exponential, tangent, and so on
  • It is high performance numeric data processor. It can multiply two 64-bit real numbers in about 27 microseconds and calculate square root in about 36 microseconds.
  • It follows IEEE floating point standard.
  • It is multibus compatible.