1. Computer Architecture CPSC 350
E. J. Kim

2. Course Contents

3. Course Contents Organization of a computer Assembly language
Design of a computer
Verilog
Future architectures

4. How does the course fit into the curriculum?
CPSC 4xx compiler OS
CPSC 483 Computer Sys Design
CPSC 350 Computer Architecture
ELEN 220 Intro to Digital Design
ELEN 248 Intro to DGTL Sym Design

5. Syllabus
Two exams 50%
Assignments and quizzes 20%
Projects 30%

6. Course Information Labs MIPS (Assembly Programming), Verilog (HDL)
Projects
Project 1: MIPS
Projects 2 & 3: Verilog (Datapath Design) TA
Lei Wang
Peer Teacher: Molly Hicks

7. Course Information [contd…]
Course Webpage
CS Accounts
Use your CS accounts to turnin and check any regarding course

8. Computer Architecture
Some people define computer architecture as the combination of
the instruction set architecture
(what the executable can see of the hardware, the functional interface)
and the machine organization
(how the hardware implements the
instruction set architecture)

9. What is Computer Architecture ?
Applications
Instruction set architecture
Machine organization
Operating
System
Compiler
Firmware
Instr. Set Proc.
I/O system
Datapath & Control
Digital Design
Circuit Design
Layout
Many levels of abstraction

10. Factors affecting ISA ??? Technology Cleverness Applications History
Programming
Languages
Applications
Computer
Architecture
Cleverness
Operating
Systems
History

11. ISA: Critical Interface
software
instruction set
hardware
Examples: 80x86 50,000,000 vs. MIPS 5500,000 ???

12. The Big Picture Since 1946 all computers have had 5 components!!!
Processor
Input
Control
Memory
Datapath
Output
Since 1946 all computers have had 5 components!!!

13. Technology Trends Processor logic capacity: about 30% per year
clock rate: about 20% per year
Memory
DRAM capacity: about 60% per year (4x every 3 years)
Memory speed: about 10% per year
Cost per bit: improves about 25% per year
Disk
capacity: about 60% per year
Total use of data: 100% per 9 months!
Network Bandwidth
Bandwidth increasing more than 100% per year!

14. Technology Trends Microprocessor Logic Density DRAM chip capacity DRAM
Year Size Kb Kb Mb Mb Mb Mb Mb Gb
In ~1985 the single-chip processor (32-bit) and the single-board computer emerged
In the timeframe, these may well look like mainframes compared single-chip computer (maybe 2 chips)

15. Technology Trends Smaller feature sizes – higher speed, density
ECE/CS 752; copyright J. E. Smith, 2002 (Univ. of Wisconsin)

16. Technology Trends Number of transistors doubles every 18 months
(amended to 24 months)
ECE/CS 752; copyright J. E. Smith, 2002 (Univ. of Wisconsin)

17. Levels of Representation
High Level Language Program
temp = v[k];
v[k] = v[k+1];
v[k+1] = temp;
Compiler
Assembly Language Program
lw $15, 0($2)
lw $16, 4($2)
sw $16, 0($2)
sw $15, 4($2)
Assembler
Machine Language Program
Machine Interpretation
Control Signal Specification
ALUOP[0:3] <= InstReg[9:11] & MASK

18. Execution Cycle Instruction Fetch
Decode
Operand
Execute
Result
Store
Next
Obtain instruction from program storage
Determine required actions and instruction size
Locate and obtain operand data
Compute result value or status
Deposit results in storage for later use
Determine successor instruction

19. What next? How does better technology help to improve performance?
How can we quantify the gain?
The MIPS architecture
MIPS instructions
First contact with assembly language programming

20. The Role of Performance

21. Performance
Response time: time between start and finish of the task (aka execution time)
Throughput: total amount of work done in a given time

22. Question
Suppose that we replace the processor in a computer by a faster model
Does this improve the response time?
How about the throughput?

23. Question
Suppose we add an additional processor to a system that uses separate processors for separate tasks.
Does this improve the response time?
Does this improve the throughput?

24. CPU Performance CPU Execution time for a program
= CPU Clock Cycles for a program
X Clock Cycle time
= CPU Clock Cycles for a program /
Clock rate

25. CPU Performance Example
A program runs in 10 secs on computer A with a 4 GHz clock. We try to build computer B, that runs this program in 6 secs where computer B requires 1.2 times as many clock cycles as computer A for this program. What clock rate should we target?

26. CPU Performance CPU clock cycles = instruction count X CPI CPU time
= instruction count X CPI X Clock cycle time
inst count
Cycle time
CPI

27. Cycles Per Instruction (Throughput)
“Average Cycles per Instruction”
CPI = (CPU Time * Clock Rate) / Instruction Count
= Cycles / Instruction Count
“Instruction Frequency”

28. Example: Calculating CPI
Base Machine (Reg / Reg)
Op Freq Cycles CPI(i) (% Time)
ALU 50% (33%)
Load 20% (27%)
Store 10% (13%)
Branch 20% (27%)
1.5
Typical Mix of
instruction types
in program

29. " X is n times faster than Y" means
Performance
(Absolute) Performance
Relative Performance
" X is n times faster than Y" means
n =

30. MIPS as a performance measure
MIPS = Instruction count
/ (Execution time X 10^6)
Ex P. 269

31. Amdahl’s Law
The execution time after making an improvement to the system is given by
Exec time after improvement = I/A + E
I = execution time affected by improvement
A = amount of improvement
E = execution time unaffected

32. Amdahl’s Law
Suppose that program runs 100 seconds on a machine and multiplication instructions take 80% of the total time. How much do I have to improve the speed of multiplication if I want my program to run 5 times faster?
20 seconds = 80 seconds/n + 20 seconds
=> it is impossible!