Computer Organization and
Architecture - Definitions
Functional levels
Definition of Computer Architecture
Computer Systems Organization – Basics:
•Processors;
•Main Memory;
•Secondary Memory;
•Peripherals: graphical, audio, printers;
•Networking.
Dr.Iliya Georgiev
1
6/21/2016
Functional levels diagram (T fig.1-2)
Problem-oriented language level
Translation
Assembly Language level
Operating System Machine Level
Partial Interpretation
Instruction Set Architecture Level
Micro architecture Level
Digital Logic Level
Microprogram Interpretation
Hardware
Digital Logic Level
Based on the Boolean algebra
 Gates: AND, OR, XOR,…
 Digital Devices: coder, decoder, latch,
memory element,…
 Implementation:
- mostly by electronic devices;
- weird: pneumatic devices,…

Dr.Iliya Georgiev
3
6/21/2016
Microarchitecture Level
Arithmetic Logic Unit
 Register Block (File)
 Memories (cache, Main)
 Information Path
 Control:
- microoperations and micro programs;
- finite state machine.

Dr.Iliya Georgiev
4
6/21/2016
Instruction Set Architecture Level
Instruction Set
 Data Formats
 Principles of Operations

Dr.Iliya Georgiev
5
6/21/2016
OS Machine Level
Virtual Memory
 BIOS
 Virtual Instructions
 Virtual Machine Idea
 Process and Treads Management
 Virtual Instruction Set for Networking or
Parallel Processing

Dr.Iliya Georgiev
6
6/21/2016
Assembly Language level
Assembler language is a symbolic form of
machine language together with some
macroinstructions and procedures.
 Programs can be written for lower levels
with full access to the computer resources.
 Compiler from assembly programs is
called Assembler.

Dr.Iliya Georgiev
7
6/21/2016
Problem-oriented language level
High level languages:
Programming languages (Java, C++, Lisp,
Prolog, Pascal, Fortran,…);
 Data description languages (HTML,
XML,…).
 Procedural Languages (so called scripts) –
Java script, VB script, …

Dr.Iliya Georgiev
8
6/21/2016
Computer Architecture
– classical definition
Data Formats
 Instruction Set
 Principle of Operation (textual or formal

description of every operation)

Features (virtual memory, direct memory access,
interrupt mechanism, etc.)
Dr.Iliya Georgiev
9
6/21/2016
Some historical architecture terms
1. Von Neumann architecture (both programs and
data are stored in the same memory)-T fig.1-5
CPU (mill)
Memory (programs + data)
2. Harvard architecture
CPU
Program memory
Data Memory
Dr.Iliya Georgiev
10
6/21/2016
Computer Structure:
Digital Blocks and Devices:
 processor,
 memories,
 display (video) subsystem,
 hard drives,
 CD drives, etc.
Data Buses
Interfaces (serial, parallel, LAN,…)
Dr.Iliya Georgiev
11
6/21/2016
Computer Structure
CPU1
CPU n
Main
Memory
LAN
System Bus (Hierarchy of Buses)
Disk
Controller
Video
Subsystem
Interfaces
Audio
Parallel
Serial (LPT)
(COM)
Dr.Iliya Georgiev
12
6/21/2016
CPU
Executes programs stored in the main
memory by fetching their instructions,
examining them,and then executing one
after another.
 Every CPU has its unique instruction set.
 According to the instruction sets and other
features two types are recognized:
- RISC (Reduced Instruction Set
Computer);
- CISC (Complex Instruction Set
Computer);

Dr.Iliya Georgiev
13
6/21/2016
CPU blocks
Processing Block
ALU
Registers
Control Unit
Control
Signals
Clock
Clock
Generator
Signals
Dr.Iliya Georgiev
14
6/21/2016
CPU Performance Measurement
(all in metric system)

MIPS – million instructions per second
(usually integer arithmetic operations as well load/store
instructions are considered)

MFLOPS – million floating point
operations per second (one floating point
instruction combines several operations)
Dr.Iliya Georgiev
15
6/21/2016
CPU Clock as performance measurement
Main formula:
f [Hz]= 1 / T [sec],
where f – frequency, T – period.
1 Hz is one pulsation per second.
Example: Pentium 300 MHz means that the
system clock of the processor is
300,000,000 signals/sec
Dr.Iliya Georgiev
16
6/21/2016
Metric Prefixes
Frequency: 1 KHz (kilo)= 10 3 Hz;
1 MHz (mega)= 10 6 Hz;
1 GHz (giga)= 10 9Hz.
Period:
Dr.Iliya Georgiev
1 msec (milli)= 10 -3 sec;
1 µsec (micro)= 10 -6 sec;
1 nsec (nano)= 10 –9 sec;
1 psec (pico)= 10 –12 sec;
17
6/21/2016