COMP375 Practice Final Exam
You are allowed one and only one 8½ by 11 inch page of notes during this exam. You are not allowed to use more than 187 square inches
of paper surface to hold your notes. Telephone calls and texting are not allowed during the exam.
The following table represents the microcode for the simple CPU shown above. Each column represents the possible setting
of the switches shown as small circles in the diagram. The possible ALU functions are ADD, SUB, AND, OR, DECrement
by 1 and INCrement by 1. The possible memory functions are READ, WRITE, and WAIT.
1. [8 points] add R2, 47 Add the constant to R2. Show the instruction fetch and program counter
incrementation.
bus
 IR
2.
IRadr
bus
result
bus
bus
ALU
bus
oprnd
bus
PC
PC
bus
bus
R1
R1 
bus
bus
R2
R2 
bus
bus
MAR
bus
MBR
MBR
bus
ALU
func
Mem
func
[7 points] return — Pop the return address from the stack and put it in the program counter.
Assume R2 is the stack pointer. Do NOT show the instruction fetch.
bus
 IR
IRadr
bus
result
bus
bus
ALU
bus
oprnd
bus
PC
PC
bus
bus
R1
R1 
bus
bus
R2
R2 
bus
bus
MAR
bus
MBR
MBR
bus
ALU
func
Mem
func
(The tables may or may not be longer than necessary.)
3. [7 points] Imagine your company has a database server that you need to keep running even if one of
the disk drives fails. The operating system uses 24 GB of space and the database requires 200 GB of
space. There is a good deal on 320 GB drives. How should you configure the server’s disks and
how many disks are required?
COMP375-001 Computer Architecture and Organization
Computer Science department of North Carolina A&T State University
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COMP375 Practice Final Exam
A bus protocol requires the CPU to put the address on the bus during the first clock period. On the
fourth clock period and every clock period afterwards data is retrieved from the RAM.
4. [10 points] Assume the system has a 256 bit wide bus. The system always reads 96 bytes at a time.
How many bus clock cycles does it take from when the CPU first requests the data until 96 bytes
have been read? (Note the diagram above may or may not show more or less cycles than necessary.)
If the bus operates at 800 MHz, how long is a single clock cycle?
How many nanoseconds does it take to read 96 bytes from the RAM?
5. [4 points] New Intel processors have a feature called Enhanced Intel SpeedStep® Technology that
reduces the system voltage and clock frequency when the system is relatively idle. Why might you
want to do this? What advantage does this provide?
6. [7 points] You just purchased a server with a RAID 5 controller that has 5 physical disk drives of
320 GB each. How much data can you store on the server?
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Computer Science department of North Carolina A&T State University
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COMP375 Practice Final Exam
7. [12 points] Write a program in Intel assembler to perform the equivalent calculations as shown in
C++.
int horse, mule, donkey;
cin >> horse >> mule >> donkey; // reads data in C++
_asm {
/*
write this part in assembler
horse = donkey * (mule + horse);
mule++;
if ( mule > 42 ) {
donkey = 23;
} else {
donkey = 12;
}
*/
}
cout << horse << mule << donkey << endl;
8. [8 points] Consider a system with a 64 bit address space, 4 MB cache with 64 byte lines using direct
mapping. Divide the address below labeling each part of the address and specify the size of each
field in bits.
COMP375-001 Computer Architecture and Organization
Computer Science department of North Carolina A&T State University
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COMP375 Practice Final Exam
Rotational Speed
Average Read Seek Time
Track-To-Track Seek Time
Full Stroke Seek
Cylinders
Number of Heads (Physical)
Sectors Per Track
Bytes Per Sector
15,000 RPM
4.8 ms
2.0 ms
19.2 ms
32,767
4
63
512
9. [10 points] How long, on the average, will it take to read a 24 KB file from the above disk assuming
all blocks are stored together on a track?
10. [9 points] A memory system has RAM with an access time of 54.0 nsec and cache memory with an
access time of 4.8 nsec. If the system gets an average hit rate of 91%, what is the average memory
access time?
11. [2 points] Roughly how many nanoseconds are there in a millisecond?
COMP375-001 Computer Architecture and Organization
Computer Science department of North Carolina A&T State University
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COMP375 Practice Final Exam
12. [8 points] Explain the two different forms of the locality of reference.
13. [8 points] Explain how locality of reference and the memory
hierarchy work together to improve system performance.
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Computer Science department of North Carolina A&T State University
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