CS 2734 Computer Organization II

• Informal Quiz 2: Tracing Instruction Cycle
  (I'll hand this out today, but I'll show you the answer in class on Monday.)

• Another example of two-stage pipelining to illustrate the roles of the pc and the npc.

• Ask for C questions relevant to laboratory 4:
  • You open a data file with code such as:

             fp = fopen("my.file", "r");
    

    Remember to check to make sure that fp is not NULL after this is executed. Also, do not hardcode in the file name -- you are passing it in on the command line.

  • You can allocate space with malloc or calloc. For example to allocate an array of 10 doubles:

            double *f;
    
            f = (double *)calloc(10, sizeof(double));
            if (f == NULL) {
               fprintf(stderr, "failed to allocate space for f\n");
               exit(1);
            }
    

    You of course will be allocating an array of int rather than double and will be getting the number of elements from the command line.

  • You read in values from a file using fscanf. For example:

            fscanf(fp, "%lf", &(f[i]));
    

    reads the next value from the file fp into the array element f[i].

• Discuss laboratory check off policy:
  For the Monday lab, Ms. Dykes will check off for the 45 minutes. There will be a signup sheet. You must have actually gone through the check off procedure yourself before asking to be checked off. If you are not ready, you'll have to go to the end of the line. After the first 45 minutes and through her office hour, Ms. Dykes will be available for help with problems. She cannot do the assignment for you. If you can't get started you should come to see me. The Wednesday lab will be for check off and help will be available only if there is no one waiting to be checked off. If you don't have the assignment completely working you can ask for partial checkoff but you need to be prepared to demonstrate the part that you want checked off.

• Strategy for laboratory 4 - develop and debug in stages:
  • Write the program and the function in C. The function will be in a separate file. (This allows you to debug the C driver without worrying about the Sparc. You will also get your makefile working.)

  • Replace the file with the C function for calsigndot with a Sparc function. This version should only compute the sum of the elements. (This allows you to make sure that you are passing the parameters correctly.)

  • Insert the full function.

• Accessing a one-dimensional array in Sparc when the starting address is in a register.
  • One dimensional array addressing in general for array element A[i] is done by calculating the address of that element:

          address of A[i] = start of A + i*(size of each element)
    

  • For arrays of integers, the size of each element is 4. If you have the starting address of the array in a register, just add 4 to the register each time. (We'll do some examples in class.)