Secondary memory and DMA

Question 1

If the numerical value of a 2-byte unsigned integer on a little endian computer is 255 more than that on a big endian computer, which of the following choices represent(s) the unsigned integer on a little endian computer?

• 0x6665
• 0x0001
• 0x4243
• 0x0100

Question 2

On a non-pipelined sequential processor, a program segment, which is a part of the interrupt service routine, is given to transfer 500 bytes from an I/O device to memory.

              Initialize the address register
              Initialize the count to 500
        LOOP: Load a byte from device
              Store in memory at address given by address register
              Increment the address register
              Decrement the count
              If count != 0 go to LOOP 

Assume that each statement in this program is equivalent to machine instruction which takes one clock cycle to execute if it is a non-load/store instruction. The load-store instructions take two clock cycles to execute. The designer of the system also has an alternate approach of using DMA controller to implement the same transfer. The DMA controller requires 20 clock cycles for initialization and other overheads. Each DMA transfer cycle takes two clock cycles to transfer one byte of data from the device to the memory. What is the approximate speedup when the DMA controller based design is used in place of the interrupt driven program based input-output?

• 3.4

• 4.4

• 5.1

• 6.7

Question 3

In a computer system, four files of size 11050 bytes, 4990 bytes, 5170 bytes and 12640 bytes need to be stored. For storing these files on disk, we can use either 100 byte disk blocks or 200 byte disk blocks (but can\'t mix block sizes). For each block used to store a file, 4 bytes of bookkeeping information also needs to be stored on the disk. Thus, the total space used to store a file is the sum of the space taken to store the file and the space taken to store the book keeping information for the blocks allocated for storing the file. A disk block can store either bookkeeping information for a file or data from a file, but not both. What is the total space required for storing the files using 100 byte disk blocks and 200 byte disk blocks respectively?

• 35400 and 35800 bytes

• 35800 and 35400 bytes

• 35600 and 35400 bytes

• 35400 and 35600 bytes

Question 4

The size of the data count register of a DMA controller is 16 bits. The processor needs to transfer a file of 29,154 kilobytes from disk to main memory. The memory is byte addressable. The minimum number of times the DMA controller needs to get the control of the system bus from the processor to transfer the file from the disk to main memory is _________   Note : This question was asked as Numerical Answer Type.

• 3644
• 3645
• 456
• 1823

Question 5

Which of the following DMA transfer modes and interrupt handling mechanisms will enable the highest I/O band-width?  

• Transparent DMA and Polling interrupts

• Cycle-stealing and Vectored interrupts

• Block transfer and Vectored interrupts

• Block transfer and Polling interrupts

Question 6

Which of the following systems is a most likely candidate example of a pipe and filter architecture ?

• Expert system
• DB repository
• Aircraft flight controller
• Signal processing

Question 7

The main difference(s) between a CISC and a RISC processor is/are that a USC processor typically: a) has fewer instructions b) has fewer addressing modes c) has more registers d) is easier to implement using hardwired control logic

• a and b
• b and c
• a and d
• a, b, c and d

Question 8

The address space of 8086 CPU is

• One Megabyte
• 256 Kilobytes
• 1 K Megabytes
• 64 Kilobytes

Question 9

If an instruction takes i microseconds and a page fault takes an additional j microseconds, the effective instruction time if on the average a  page fault occurs every k instructions is:

• i + j/k
• i + j* k
• (i + j)/ k
• (i + j)* k

Question 10

The correct matching for the following pairs is

(A) DMA I/O                    (1) High speed RAM
(B) Cache                      (2) Disk
(C) Interrupt I/O              (3) Printer
(D) Condition Code Register    (4) ALU

Codes:
    A   B   C   D 
a   4   3   1   2
b   2   1   3   4
c   4   3   2   1
d   2   3   4   1

• a
• b
• c
• d