COE 308 – Computer Architecture
Exam I – Fall 2008
Monday, November 24, 2008
7:00 pm – 9:00 pm
Computer Engineering Department
College of Computer Sciences & Engineering
King Fahd University of Petroleum & Minerals
Student Name:
Student ID:
Q1
/ 10
Q2
/ 10
Q3
/ 20
Q4
/ 20
Q5
/ 20
Q6
/ 25
Total
/ 105
Important Reminder on Academic Honesty
Using unauthorized information on an exam, peeking at others work, or altering
graded exams to claim more credit are severe violations of academic honesty.
Detected cases will receive a failing grade in the course.
Prepared by Dr. Muhamed Mudawar
Page 1 of 7
Page 2 of 7
Q1. a) (5 pts) A wafer containing 100 copies of a 2 cm2 die costs $900 to manufacture. The
defect density is 2/cm2. What is the manufacturing cost of a good die? The die yield is
given by the following formula: Die yield = [1 + (Defect density × Die area)/3]-3
b)
(5 pts) If the die area is reduced from 2 cm2 to 1 cm2, what will be manufacturing cost of
the smaller 1 cm2 die?
Q2. Given the bit pattern of a single-precision floating-point number:
11000110110101000000000000000000 (binary)
a)
(4 pts) What is the decimal value of the above number?
b)
(6 pts) Show the single precision representation for -0.05, rounded to the nearest even.
Page 3 of 7
Q3. (20 pts) Write a minimal sequence of real MIPS instructions to:
a)
(4 pts) Produce a carry bit in $t0 that results from the addition of $s0 and $s1.
b)
(6 pts) Produce an overflow bit in $t0 from the addition of $s0 and $s1. Hint:
overflow occurs if $s0 and $s1 have the same sign, but their sum has a different sign.
c)
(5 pts) Swap the content of registers $s0 and $s1 without disturbing the content of any
other register. Hint: (x  y)  y = x
d)
(5 pts) Rotate left the content of registers $s0 by 7 bits and put the result in register in
register $t0. Only register $at can be used for intermediate results.
Page 4 of 7
Q4. a) (8 pts) The following code computes a result in register $s1, when given a positive
integer N in register $s0. Describe what the code does and what will be returned in
register $s1. How many instructions are executed in all iterations in terms of N?
loop:
done:
b)
add
addi
addi
addi
add
beq
addi
j
add
$t2,
$t2,
$t0,
$t1,
$t0,
$t1,
$t1,
loop
$s1,
$s0, $s0
$t2, 1
$zero, 0
$zero, 1
$t0, $t1
$t2, done
$t1, 2
$zero, $t0
(12 pts) The following code fragment processes two arrays and produces a result in
register $v0. Assume that each array consists of N words, the base addresses of the
arrays are stored in $a0 and $a1 respectively, and their size (N) is stored in $a2.
Describe what the code does and what will be returned in $v0. How many instructions
are executed in all iterations in terms of N?
sll
add
add
outer: add
lw
add
inner: add
lw
bne
addi
skip: addi
bne
addi
bne
$a2,
$v0,
$t0,
$t4,
$t4,
$t1,
$t3,
$t3,
$t3,
$v0,
$t1,
$t1,
$t0,
$t0,
$a2, 2
$zero, $zero
$zero, $zero
$a0, $t0
0($t4)
$zero, $zero
$a1, $t1
0($t3)
$t4, skip
$v0, 1
$t1, 4
$a2, inner
$t0, 4
$a2, outer
Page 5 of 7
Q5. (20 pts) Given that x = 1 10000101 101100000000000000000012 and
y = 1 01111111 010000000000000001000002 are single precision IEEE 754
floating-point numbers. Perform the following operations showing all the intermediate
steps and final result in binary. Round to the nearest even.
a)
b)
(10 pts) x + y
(10 pts) x * y
Page 6 of 7
Q6. (25 Pts) Write MIPS assembly code for the procedure BinarySearch to search an array
which has been previously sorted. Each element in the array is a 32-bit signed integer.
The procedure receives three parameters: register $a0 = address of array to be
searched, $a1 = size (number of elements) in the array, and $a2 = item to be searched. If
found then BinarySearch returns in register $v0 = address of the array element where
item is found. Otherwise, $v0 = 0.
BinarySearch ($a0=array, $a1=size, $a2=item) {
lower = 0;
upper = size-1;
while (lower <= upper) {
middle = (lower + upper)/2;
if (item == array[middle])
return $v0 = ADDRESS OF array[middle];
else if (item < array[middle])
upper = middle–1;
else
lower = middle+1;
}
return $v0=0;
}
Page 7 of 7
Additional Page if Needed