Intel 8085 & 8086 interview questions

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					8085 microprocessor questions

   1. What are the various registers in 8085? - Accumulator
      register, Temporary register, Instruction register, Stack
      Pointer, Program Counter are the various registers in 8085 .

   2. In 8085 name the 16 bit registers? - Stack pointer and
      Program counter all have 16 bits.

   3. What are the various flags used in 8085? - Sign flag, Zero
      flag, Auxillary flag, Parity flag, Carry flag.

   4. What is Stack Pointer? - Stack pointer is a special purpose
      16-bit register in the Microprocessor, which holds the address
      of the top of the stack.

   5. What is Program counter? - Program counter holds the
      address of either the first byte of the next instruction to be
      fetched for execution or the address of the next byte of a multi
      byte instruction, which has not been completely fetched. In
      both the cases it gets incremented automatically one by one as
      the instruction bytes get fetched. Also Program register keeps
      the address of the next instruction.

   6. Which Stack is used in 8085? - LIFO (Last In First Out) stack
      is used in 8085.In this type of Stack the last stored information
      can be retrieved first.

   7. What happens when HLT instruction is executed in
      processor? - The Micro Processor enters into Halt-State and
      the buses are tri-stated.

   8. What is meant by a bus? - A bus is a group of conducting
      lines that carriers data, address, & control signals.

   9. What is Tri-state logic? - Three Logic Levels are used and
      they are High, Low, High impedance state. The high and low
      are normal logic levels & high impedance state is electrical
      open circuit conditions. Tri-state logic has a third line called
      enable line.

   10. Give an example of one address microprocessor? - 8085 is a
       one address microprocessor.

   11. In what way interrupts are classified in 8085? - In 8085 the
       interrupts are classified as Hardware and Software interrupts.

   12. What are Hardware interrupts? - TRAP, RST7.5, RST6.5,
   RST5.5, INTR.

13. What are Software interrupts? - RST0, RST1, RST2, RST3,
    RST4, RST5, RST6, RST7.

14. Which interrupt has the highest priority? - TRAP has the
    highest priority.

15. Name 5 different addressing modes? - Immediate, Direct,
    Register, Register indirect, Implied addressing modes.

16. How many interrupts are there in 8085? - There are 12
    interrupts in 8085.

17. What is clock frequency for 8085? - 3 MHz is the maximum
    clock frequency for 8085.

18. What is the RST for the TRAP? - RST 4.5 is called as

19. In 8085 which is called as High order / Low order
    Register? - Flag is called as Low order register &
    Accumulator is called as High order Register.

20. What are input & output devices? - Keyboards, Floppy disk
    are the examples of input devices. Printer, LED / LCD display,
    CRT Monitor are the examples of output devices.

21. Can an RC circuit be used as clock source for 8085? - Yes,
    it can be used, if an accurate clock frequency is not required.
    Also, the component cost is low compared to LC or Crystal.

22. Why crystal is a preferred clock source? - Because of high
    stability, large Q (Quality Factor) & the frequency that doesn¶t
    drift with aging. Crystal is used as a clock source most of the

23. Which interrupt is not level-sensitive in 8085? - RST 7.5 is a
    raising edge-triggering interrupt.

24. What does Quality factor mean? - The Quality factor is also
    defined, as Q. So it is a number, which reflects the lossness of
    a circuit. Higher the Q, the lower are the losses.

25. What are level-triggering interrupt? - RST 6.5 & RST 5.5
    are level-triggering interrupts.
x86 interview questions

These interview questions test the
knowledge of x86 Intel architecture and
8086 microprocessor specifically.

   1. What is a Microprocessor? -
      Microprocessor is a program-
      controlled device, which fetches the
      instructions from memory, decodes
      and executes the instructions. Most
      Micro Processor are single- chip

   2. Give examples for 8 / 16 / 32 bit
      Microprocessor? - 8-bit Processor -
      8085 / Z80 / 6800; 16-bit Processor
      - 8086 / 68000 / Z8000; 32-bit
      Processor - 80386 / 80486.

   3. Why 8085 processor is called an 8
      bit processor? - Because 8085
      processor has 8 bit ALU (Arithmetic
      Logic Review). Similarly 8086
      processor has 16 bit ALU.

   4. What is 1st / 2nd / 3rd / 4th
      generation processor? - The
      processor made of PMOS / NMOS /
      HMOS / HCMOS technology is
      called 1st / 2nd / 3rd / 4th generation
      processor, and it is made up of 4 / 8
      / 16 / 32 bits.

   5. Define HCMOS? - High-density n-
      type Complimentary Metal Oxide
      Silicon field effect transistor.

   6. What does microprocessor speed
      depend on? - The processing speed
      depends on DATA BUS WIDTH.

   7. Is the address bus unidirectional?
      - The address bus is unidirectional
      because the address information is
      always given by the Micro
      Processor to address a memory
   location of an input / output devices.

8. Is the data bus is Bi-directional? -
   The data bus is Bi-directional
   because the same bus is used for
   transfer of data between Micro
   Processor and memory or input /
   output devices in both the direction.

9. What is the disadvantage of
   microprocessor? - It has limitations
   on the size of data. Most
   Microprocessor does not support
   floating-point operations.

10. What is the difference between
    microprocessor and
    microcontroller? - In
    Microprocessor more op-codes, few
    bit handling instructions. But in
    Microcontroller: fewer op-codes,
    more bit handling Instructions, and
    also it is defined as a device that
    includes micro processor, memory,
    & input / output signal lines on a
    single chip.

11. What is meant by LATCH? -
    Latch is a D- type flip-flop used as a
    temporary storage device controlled
    by a timing signal, which can store 0
    or 1. The primary function of a
    Latch is data storage. It is used in
    output devices such as LED, to hold
    the data for display.

12. Why does microprocessor contain
    ROM chips? - Microprocessor
    contain ROM chip because it
    contain instructions to execute data.

13. What is the difference between
    primary & secondary storage
    device? - In primary storage device
    the storage capacity is limited. It has
    a volatile memory. In secondary
    storage device the storage capacity
   is larger. It is a nonvolatile memory.
   Primary devices are: RAM / ROM.
   Secondary devices are: Floppy disc /
   Hard disk.

14. Difference between static and
    dynamic RAM? - Static RAM: No
    refreshing, 6 to 8 MOS transistors
    are required to form one memory
    cell, Information stored as voltage
    level in a flip flop. Dynamic RAM:
    Refreshed periodically, 3 to 4
    transistors are required to form one
    memory cell, Information is stored
    as a charge in the gate to substrate

15. What is interrupt? - Interrupt is a
    signal send by external device to the
    processor so as to request the
    processor to perform a particular

16. What is cache memory? - Cache
    memory is a small high-speed
    memory. It is used for temporary
    storage of data & information
    between the main memory and the
    CPU (center processing unit). The
    cache memory is only in RAM.

17. What is called ³Scratch pad of
    computer´? - Cache Memory is
    scratch pad of computer.

18. Which transistor is used in each
    cell of EPROM? - Floating ±gate
    Avalanche Injection MOS
    (FAMOS) transistor is used in each
    cell of EPROM.

19. Differentiate between RAM and
    ROM? - RAM: Read / Write
    memory, High Speed, Volatile
    Memory. ROM: Read only memory,
    Low Speed, Non Voliate Memory.
   20. What is a compiler? - Compiler is
       used to translate the high-level
       language program into machine
       code at a time. It doesn¶t require
       special instruction to store in a
       memory, it stores automatically. The
       Execution time is less compared to

   21. Which processor structure is
       pipelined? - All x86 processors
       have pipelined structure.

   22. What is flag? - Flag is a flip-flop
       used to store the information about
       the status of a processor and the
       status of the instruction executed
       most recently

   23. What is stack? - Stack is a portion
       of RAM used for saving the content
       of Program Counter and general
       purpose registers.

   24. Can ROM be used as stack? -
       ROM cannot be used as stack
       because it is not possible to write to

   25. What is NV-RAM? - Nonvolatile
       Read Write Memory, also called
       Flash memory. It is also know as
       shadow RAM.

Intel interview questions

   1. The following questions are used
      for screening the candidates
      during the first interview. The
      questions apply mostly to fresh
      college grads pursuing an
      engineering career at Intel.
          1. Have you studied buses?
              What types?

          2. Have you studied pipelining?
   List the 5 stages of a 5 stage
   pipeline. Assuming 1 clock
   per stage, what is the latency
   of an instruction in a 5 stage
   machine? What is the
   throughput of this machine ?

3. How many bit combinations
   are there in a byte?

4. For a single computer
   processor computer system,
   what is the purpose of a
   processor cache and describe
   its operation?

5. Explain the operation
   considering a two processor
   computer system with a
   cache for each processor.

6. What are the main issues
   associated with
   multiprocessor caches and
   how might you solve them?

7. Explain the difference
   between write through and
   write back cache.

8. Are you familiar with the
   term MESI?

9. Are you familiar with the
   term snooping?

10. Describe a finite state
    machine that will detect
    three consecutive coin tosses
    (of one coin) that results in

11. In what cases do you need to
    double clock a signal before
    presenting it to a
    synchronous state machine?

12. You have a driver that drives
   a long signal & connects to
   an input device. At the input
   device there is either
   overshoot, undershoot or
   signal threshold violations,
   what can be done to correct
   this problem?

13. What are the total number of
    lines written by you in
    C/C++? What is the most
    program written in C/C++?

14. What compiler was used?

15. What is the difference
    between = and == in C?

16. Are you familiar with VHDL
    and/or Verilog?

17. What types of CMOS
    memories have you
    designed? What were their
    size? Speed?

18. What work have you done
    on full chip Clock and Power
    distribution? What process
    technology and budgets were

19. What types of I/O have you
    designed? What were their
    size? Speed? Configuration?
    Voltage requirements?

20. Process technology? What
    package was used and how
    did you model the
    package/system? What
    parasitic effects were

21. What types of high speed
    CMOS circuits have you

          22. What transistor level design
              tools are you proficient
              with? What types of designs
              were they used on?

          23. What products have you
              designed which have entered
              high volume production?

          24. What was your role in the
              silicon evaluation/product
              ramp? What tools did you

          25. If not into production, how
              far did you follow the design
              and why did not you see it
              into production?

A+ and basic PC questions

   1. What are the basic expansion card
      types?ISA and PCI, ISA can be
      used only on XT, AT and ATX
      boards. The industry now considers
      ISA obsolete.

   2. How do you clear CMOS
      password? Since CMOS is a special
      chip with its own battery, the best
      way to clear out a CMOS chip is to
      disconnect it from its power supply.

   3. Where does the Real mode on the
      CPU come from? The original
      8086, which only had 1 MB of
      memory. This megabyte is split into
      low memory for IRQ tables,
      application memory and high

   4. Where does CPU Enhanced mode
      originate from? Intel¶s 80386 was
      the first 32-bit processor, and since
      the company had to backward-
   support the 8086. All the modern
   Intel-based processors run in the
   Enhanced mode, capable of
   switching between Real mode (just
   like the real 8086) and Protected
   mode, which is the current mode of

5. Name the processor lines of two
   major manufacturers? High-end:
   Intel - Pentium (II, III, 4), AMD -
   Athlon. Low-end: Intel - Celeron,
   AMD - Duron. 64-bit: Intel -
   Itanium 2, AMD - Opteron.

6. What¶s the difference between L1
   and L2 cache? Level 1 cache is
   internal to the chip, L2 is external.

7. What¶s the speed and device
   maximum specs for Firewire?
   IEEE 1394 (Firewire) supports the
   maximum of 63 connected devices
   with speeds up to 400 Mbps.

8. Where¶s MBR located on the
   disk? Main Boot Record is located
   in sector 0, track 0, head 0, cylinder
   0 of the primary active partition.

9. What¶s the maximum hard drive
   size for FAT16-based Windows
   system? 2 GB.

10. How many logical drives is it
    possible to fit onto a physical
    disk? Maximum of 24 logical
    drives. The extended partition can
    only have 23 logical drives.

11. WHat are * and ? when using
    them for wildcards in Windows? *
    - any characters, arbitrary amoung, ?
    - single character.

12. How does the browser know to go
    to a certain IP address when you
    enter a domain like It
         searches through local DNS cache,
         if nothing is there, it queries the
         ISP¶s DNS server.

Telecommunications interview questions

A well-known telecommunications company uses this pop quiz for
oral and written examinations of applicants for engineering positions.

1. A 2MB PCM(pulse code modulation) has«

a) 32 channels
b) 30 voice channels & 1 signaling channel.
c) 31 voice channels & 1 signaling channel.
d) 32 channels out of which 30 voice channels, 1 signaling channel, &
1 synchronization channel.

Ans: c

2. Time taken for 1 satellite hop in voice communication is«

a) 1/2 second
b) 1 seconds
c) 4 seconds
d) 2 seconds

Ans: (a)

3. Max number of satellite hops allowed in voice communication

a) only one
b) more han one
c) two hops
d) four hops

Ans: ©

4. What is the maximal decimal number that can be
accommodated in a byte?

a) 128
b) 256
c) 255
d) 512

Ans: ©

5. Conditional results after execution of an instruction in a micro
processor is stored in«

a) register
b) accumulator
c) flag register
d) flag register part of PSW(Program Status Word)

Ans: (d)

6. Frequency at which VOICE is sampled is«

a) 4 KHz
b) 8 KHz
c) 16 KHz
d) 64 KHz

Ans: (a)

7. Line of sight is«

a) Straight Line
b) Parabolic
c) Tx & Rx should be visible to each other
d) none of the above

Ans: ©

8. Purpose of PC(Program Counter) in a MicroProcessor is«

a) To store address of TOS(Top Of Stack)
b) To store address of next instruction to be executed.
c) count the number of instructions.
d) to store base address of the stack.

Ans: (b)

9. What action is taken when the processor under execution is
interrupted by a non-maskable interrupt?

a) Processor serves the interrupt request after completing the
execution of the current instruction.
b) Processor serves the interrupt request after completing the current
c) Processor serves the interrupt request immediately.
d) Processor serving the interrupt request depends upon the priority of
the current task under execution.

Ans: (a)

10. The status of the Kernel is«

a) task
b) process
c) not defined.
d) none of the above.

Ans: (b)

11. What is the nominal voltage required in subscriber loop
connected to local exchange?

a) +48 volts
b) -48 volts
c) 230 volts
d) 110 volts

12. To send a data packet using datagram , connection will be

a) before data transmission.
b) connection is not established before data transmission.
c) no connection is required.
d) none of the above.

Ans: ©

13. Word alignment is«

a) aligning the address to the next word boundary of the machine.
b) aligning to an even boundary.
c) aligning to a word boundary.
d) none of the above.

Ans: (a)

14. When a C function call is made, the order in which parameters
passed to the function are pushed into the stack is«

a) left to right
b) right to left
c) bigger variables are moved first than the smaller variales.
d) smaller variables are moved first than the bigger ones.
e) none of the above.

Ans: (b)

15. What is the type of signaling used between two exchanges?

a) inband
b) common channel signaling
c) any of the above
d) none of the above.

Ans: (a)

16. Buffering is«

a) the process of temporarily storing the data to allow for small
variation in device speeds
b) a method to reduce cross talks
c) storage of data within transmitting medium until the receiver is
ready to receive.
d) a method to reduce routing overhead.

Ans: (a)

17. Memory allocation of variables declared in a program is«

a) allocated in RAM.
b) allocated in ROM.
c) allocated on stack.
d) assigned to registers.

Ans: ©

18. A software that allows a personal computer to pretend as a
computer terminal is «

a) terminal adapter
b) bulletin board
c) modem
d) terminal emulation

Ans: (d)

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