The Rest of Computer Systems

Current Trends in Computer Hardware
Processor speeds are increasing
Clock speed is increasing
Increasing memory (Main memory and Backing Storage)
Data Transfer speeds increasing

4 measures to compare computer performance
Application Based Tests
involves benchmarking, getting computer systems to carry out the same tasks and measuring their performance, allows a fair comparison as it measures the performance of the whole computer system

Clock Speed
indicates the speed of the processor (Hertz!) gives an idea of how quickly the computer system executes instructions

MIPS - Millions of Instructions per second
not a fair method of comparison as computer systems have different instruction sets and carry out instrcutions in different ways

FLOPS - Floating Point Operations Per Second
measures how quikcly a computer can perform complex calcualations. these can be compared as the computer systems carry them out in the same method.

Cache memoire!!!!

Faster to access than main memory
stores the most commonly used instructions (don't need to fetch from main memory)
physically closer to main memory

Computer Structure

Read Operation
1. CU Set up MAR with the address to be accessed
2. Control unit activates the Read Line
3. Storage location info. are released onto the Databus
4. Copy is transferred into the MDR

(MAR - Memory Address Register, MDR - Memory Data Register)
The Fetch Execute Cycle (Get it, Dae it!) is an important process in the computer system
a. Fill in the missing steps

1. __________________________________________________
2. Control Unit Activates the read line
3. contents are ________________________________________
4. copy of the information ________________________________
5. instruction is decoded and ______________________________


1. SAME AS READ STEP 1
3. SAME AS READ STEP 3
4. SAME AS READ STEP 4
5. EXECUTED!


Write Operation
1. CU sets up MAR with the address to be accessed
2. CU sets up MDR with data to be written
3. CU activates the write line
4. Data is transferred to mem. location via the Data Bus.

Computer Structure

The Processor's three main parts ... C U A Love U Right!

CU- Control Unit
controls the other parts of the processor, makes sure instructions are carried out in the correct order
ALU - Arithmetic Logic Unit
carries out calculations, makes decisions based on logic (and or not)
R- Registers

temporary storage locations used to store addresses to be accessed and data to be written or read
Two of the three buses on the Computer System

Address Bus - (one way) unidirectional, carry the address to be accessed in memory (goes and points at a mem. location) number of wires tells you how many addresses can be accessed. No effect on computer system performance. (2 ^ width = number of addresses)

Data Bus - (both ways) bidirectional, carry data to and from the processor, main memory and devices. Increasing the number of bits for the data bus IMPROVES systems performance as more data can be carried per clock cycle