Cmpe 110

HomeWork 4  Floating Point and MIPS TAL

Due: Monday, Oct. 27, 2003

This assignment will test your ability in Floating point conversion and MIPS ISA. 

Floating point conversion

1.) Convert A = 1,985.2 to fixed-point binary. Use as many bits as needed for the integer portion, and use 30 bits for the significand.  Do-not round.(1 point)

2.) Express number A from ex 1) in IEEE-754 single-precision floating-point format, using the appropriate rounding method. Show all work. (2 points)

MIPS Coding and Decoding

Consider the C code below.

Assume the address for A[0] is stored $s0, address for B[0] is stored in $s1, and address for flag is stored in $s2;

Also assume these arrays were declared earlier as integer arrays (with a size of 100).  Assume integers to be 4-bytes.

int counter = 100;

int x;

for ( x = 0; x < 100; x++)

    B[x] =  1 - x;

if (flag ==1){

  while(counter != 0){

     counter--;

     A[counter] = B[counter] + counter;

   }

}

else {

while(counter != 0){

     counter--;

     A[counter] = B[counter] - 2 * counter;

   }

}

3.) Convert this snippet of C code into MIPS TAL (meaning no pseudoinstructions). (3 points)

4.) Consider the MIPS instruction code below.  Assume $s0 is the base address for 3 needed integer variables.  See problem 5, for how these variables look in memory.

            lw   $t0, 0($s0);

            lw   $t1, 4($s0);

            lw   $t3, 8($s0);

loop:    add $t1, $t1, $t0;

            addi $t1, $t1, 1 ;

            sll    $t2, $t0, 1;

            sub  $t0, $t2, $t1;

            slt   $t4, $t0, $t3;

            bne $zero, $t4, outofloop;

            j      loop;

outofloop:

Convert this MIPS TAL to C code.  Comment each line with instructions used to create the C statement on that line. (3 points)

5.)  Consider the MIPS code above.  Now consider the 2 memory blocks below.  Higher addresses go up, each block is 4 bytes or 1 word.

Use the numbers in the memory blocks, in the program above.  And find the answers to the question below.

address            Block 1                        Block2

How many times will the program loop for each given block of memory? (1/2 point each)