Computer Organization I, 2 ov, course exam 11.5.2004

There are 46 points available from the exam. (The maximum points from the exercise activity was 12 and total of 5 points were given based on the before-exercises-returned questions.)

Please try to keep your answers relatively short.

1. [12p] Execution of machine instruction and the structure of the computer
   1. [4 p] What are the different phases of the execution cycle?
   2. [1 p] How can the processor know, which machine instruction to execute next?
   3. [3 p] Define the concept interrupt (exception). What types of interrupts are there? How are interrupts handled in the processor?
   4. [4 p] What happens in the computer systen from the moment when program P, while being executed by the processor, wants to save a some data to a disk, up to the moment when P continues its execution after the I/O is finished? Please identify the I/O model used in your answer.
   
    
2. [12p] Location of the data
   Please describe all locations, from where the machine instruction can fetch the data it needs. Give examples (one per location) using ttk-91 assembler language instructions that refer to the specific locations. Explain also briefly in which phase the reference is done and how the data is found based on the information in the instruction. What are the speed differences roughly?

   (NOTICE: Omit the cache in your consideration, although it is quite often the location of the accessed data.)

3. [10 p] Hamming code
   Let us assume that there is a need to store 4 data bits 1011 (0xB) to the memory. The data bits will be protected using Hamming code with even parity.
   1. [2 p] How many parity (check) bits do you need to protect the 4 data bits?
   2. [4 p] Create the Hamming coded bit sequence to store the 4 data bits.
   3. [2 p] What would happen in the system, when the third bit of the Hamming-coded sequence flips and is, thus, changed. Bits are counted from right to left. Can you detect this error in the coded sequence? Can you fix it? Why and how? Give all necessary details.
   4. [2 p] What would happen in the system, when both the second and third bit of the Hamming-coded sequence flips and is, thus, changed. Bits are counted from right to left. Can you detect this error in the coded sequence? Can you fix it? Why and how? Give all necessary details.
   
    
4. [12p] Subprograms, functions
   1. [2 p] How are subroutines implemented at machine language level? What aspects are important in subroutine implementation?
   2. [2 p] What are the differences at machine language level in the usage of call-by-value parameters compared with call-by-reference parameters?
   3. [4 p] Function Apua(A, B, C) returns as its value the result of A*B+C. The parameters are all call-by-value parameters. Give in ttk-91 symbolic assembly language a program, that (i) reads three interger values, (ii) computes the secret apua-value using the function Apua, and (iii) finally prints out the average.
   4. [4 p] Implement the function Apua(A, B, C) given in part (c) with ttk-91 symbolic assembly language.