1. Computer Organization and Machine Language Programming CPTG 245

2. Understanding Computer Systems
Three basic questions associated with understanding computing systems:
What are computing systems used for?
How are computing systems implemented?
What are computing systems able to do and how well can they do it?

3. Computing Machines Ubiquitous ( = everywhere)
General purpose: servers, desktops, laptops, PDAs, etc.
Special purpose: cash registers, ATMs, games, telephone switches, etc.
Embedded: cars, hotel doors, printers, VCRs, industrial machinery, medical equipment, etc.
Distinguishing Characteristics
Speed
Cost
Ease of use, software support & interface
Scalability

4. This course is about: What computers consist of How to fix computers
How computers work
How they are organized internally
What are the design tradeoffs
How design affects programming and applications
How to fix computers
How to build myself one real cheap
Which one to buy
Knowing more about how a PentiumIII or PowerPC works internally

5. What is Computer Organization?
Electronic
Devices
Desired
Behavior
… a very wide gap between the intended behavior and the raw (unorganized) electronic devices.
The forerunners to modern computers attempted to assemble the raw devices (mechanical, electrical, or electronic) into a separate purpose-built machine for each desired behavior.

6. Role of General Purpose Computers
organization /
hardware
software
Electronic
Devices
General
Purpose
Computer
Desired
Behavior
We will break the gap into multiple levels and build an island in the middle.
A general purpose computer is an island that bridges the gap between the desired behavior (application) and the raw material (electronic devices).

7. Two Important Ideas Universal Computational Devices
Given enough time and memory, all computers are capable of computing exactly the same things (irrespective of speed, size or cost).
Turing’s Thesis: every computation can be performed by some “Turing Machine” - a theoretical universal computational device
(not mathematically proven, but taken to be true).
Problem Transformation
The ultimate objective is to transform a problem expressed in natural language into electrons running around a circuit!
That’s what Computer Science and Computer Engineering are all about!

8. Problem Transformation - finer breakdown
Desired Behavior:
application
Natural Language
Algorithm
Program
Machine Architecture
Devices
Micro-architecture
Logic Circuits
Raw Material:
electronic devices

9. The Program Level
Most computers run a special management program called the operating system (OS).
Application programs interface to the machine architecture via the OS.
An example:
Application Program
Operating System
Program (Software)
This lecture
PowerPoint
Windows NT
Data
Application Program
Operating System

10. The Machine Level Machine Architecture Microarchitecture Logic Circuit
This is the formal specification of all the functions a particular machine can carry out, known as the Instruction Set Architecture (ISA) (8.2.1)
Microarchitecture
The implementation of the ISA in a microprocessor - i.e. the way in which the specifications of the ISA are actually carried out. (8.2.2 – 8.2.7)
Logic Circuit
Each element of the microarchitecture is composed of simple logic circuits (chapters 2 to 6)
Devices
Finally, each logic circuit is actually built of electronic devices such as CMOS or NMOS or GaAs (etc.) transistors

11. Course Outline - What is Next?
How to represent numbers
The building blocks of computers: logic gates
The basic algorithm: the von Neumann model
An example: the LC-3 structure and language
Programming the machine: assembly language

12. The Von Neumann Model Basic components Instruction processing

13. The von Neumann Model - 1 Memory Processing Unit Input Output
MAR
MDR
ALU
TEMP
Control Unit PC IR
*keyboard
*monitor
Memory: holds the instructions and data
Processing Unit: processes the information
Control Unit: manages computer activity
Input: external information into the memory
Output: produces results for the user

14. The von Neumann Model - 3 Central Processing Unit (CPU)
ALU (Arithmetic and Logic Unit)
Generally operates on entire words of data
Some also work on subsets of words (eg. bits and bytes)
Registers:
Small, fast “on-board” storage for words
Close to the ALU (much faster access than RAM)
Control Unit
Program Counter (PC) or Instruction Pointer
Holds the address of the next instruction to be executed
Instruction Register (IR)
Holds the instruction being executed
The control unit coordinates all actions needed to execute the instruction

15. The von Neumann Model - 2 Memory (RAM) Input & Output
Each location has an address and contents
Address: set of bits that uniquely identify a memory location
(eg. 20 bits gives an address space of 220 locations)
Addressability (Byte vs. Word):
Note: a Word is the basic unit of data used by the processing unit (usually multiple bytes)
The size of the memory location referenced by a given address
Input & Output
LC3 deals only with keyboard and monitor
More details later

16. The LC-3 Data and Control Paths

17. Stopping the Computer Operating System External Control
controls the computer
when a program completes:
it exits
it returns control to the operating system
OS is ready for next command or program
External Control
kill or halt a program
reset a computer

18. The Clock The Drum Beat of the Computer
every operation happens in multiples of a clock cycles
0 volts
one clock cycle
2.9 volts
time
if the run latch is set (output Q = 1) then the clock output is the same as the clock generator
if the latch is reset (off) then the clock output is disabled
clock Q
Clock
generator
(crystal) S R
Run Latch