06 - Practice Test #1

The purpose of the Central Processing Unit (CPU) is to carry out program ____________. 
Each CPU is designed to execute a specific group of ____________, the instruction set.

Note: There are other CPU manufacturers like ARM, IBM, VIA, MCST, ELVEES, SRISA, NTC 
Module and Sun Microsystems but their CPUs usually have more specific uses (for example 
in mobile phones, cars, game consoles or in the military).

Some newer processors have ____________ _______. This means that they have many processors
built onto the same chip so that they can run many instructions at once.

1. Read data from memory and write data to memory.
2. Add one number with another.
3. Test to see if one number is bigger than another.
4. Move a number from one place to another (for example, 
from one register to another or between a register and memory).
5. Jump to another place in the instruction list.
6. Jump to another place in the instruction list but only if some test is 
true (for example, only if one number is bigger than another).
7. Allow programmers to program directly in Python or Java onto the CPU to 
carry out tasks

Even very complicated programs can be made by combining many simple 
instructions like these.

There are mainly two different types of CPUs used in modern desktop systems: 
___-bit CPUs and ___-bit CPUs. 

The instructions in a 32-bit CPU are good at handling data that is 32 bits 
in size (most instructions 'think' in 32 bits in a 32-bit CPU). Likewise, a 
64-bit CPU. 

The size of data that a CPU handles best is often called the word size of the CPU. 

Many older CPUs from the 70s, 80s and early 90s and some modern small CPUs) have 
an 8-bit or 16-bit word size.

The following are all factors that affect the performance of the CPU:

*Note: They are sometimes referred to as the 4 Cs

1.____ speed
2. number of processor _____
3. _____ size
4. ______ type.

The operating frequency of the CPU (also known as the CLOCK SPEED) determines how
fast it can process instructions.

The speed is measured in terms of Hertz, and it is usually lies in the megaHertz (MHz) 
or gigaHertz (GHz) range. A megaHertz means that the CPU can process one million 
instructions per second whereas a gigahertz CPU has the capability to process one 
billion instructions per second. In today's technology, all CPUs run in the gigahertz 
range and you seldom see CPUs with speed in the MHz range anymore.

Theoretically, a 500 MHz CPU is six times slower than a 3 GHz CPU and a 3.6 GHz CPU is
faster than a 3 GHz or a 3.4 GHz CPU. In general, the higher the frequency of a CPU, 
the faster the speed of the computer

Every computer has a 'clock'. This is a crystal that vibrates, generating 'pulses' that are 
used to control how the different components of a computer system work together. 
If you have a 800Mhz machine, it means the system clock is generating approximately 
800 million pulses every second! 

The ________________________________, the more fetch-decode-execute cycles the CPU can 
perform in a second and (very broadly) the faster your programs should go! 
(There are lots of other factors that may mean this is not the case, however)

 1. A CPU traditionally had one 'core' but processors these days might be dual-core or 
    quad-core for example. 
 
 2. A core is actually a processor with its own cache. 
 
 3. So a dual-core CPU has not one but two processors. 
 
 4. A quad core CPU has four processors
 
 5. Each 'brain' can be working on different parts of a program __________________
  and so this speeds up the overall CPU's performance.

1. Cache will store the most used (most frequently used) instructions
2. It is a lot quicker for the CPU to get data from the cache than from RAM
3. The more cache a computer has, the better the CPU will perform
4. Cache is effectively a small and extremely fast memory
5. Cache isn't exactly cheap - for instance, Intel Core i7 Extreme Processor 
   comes with a 12MB L3 cache, which also explains its hefty price tag of approx. $1,000
6. The larger the cache size, the faster the data transfer and the better the CPU 
   performance

Word size is a key factor when it comes to CPU performance.

The more bits the CPU can work with in one clock cycle, the 
faster the computer will go. 

The early commercial computers like the Spectrum ZX were 8-bit 
computers (in another words, the processor could work on 8 bits 
of data at a time). Things have moved on since the early 1980s 
and you are likely to be using either a 32-bit computer or a 
64-bit computer now.

|It's possible we will all be buying 128-bit computers in the 
very near future. 

Von Neumann architecture was first published by John von Neumann in 1945.
His computer architecture design consists of a 

1. Control Unit, 
2. Arithmetic and Logic Unit (ALU), 
3. Memory Unit, 
4. Registers and 
5. Inputs/Outputs.

Von Neumann architecture is based on the ___________ _____________ computer concept, 
where instruction data and program data are stored in the same memory.  

This design is still used in most computers produced today.

Von Neumann architecture was first published by John von Neumann in 1945.
His computer architecture design consists of a 

1. Control Unit, 
2. Arithmetic and Logic Unit (ALU), 
3. Memory Unit, 
4. Registers and 
5. Inputs/Outputs.

Von Neumann architecture is based on the ___________ _____________ computer concept, 
where instruction data and program data are stored in the same memory.  

This design is still used in most computers produced today.

Definition #1
-------------
This is where the CPU performs any mathematical sums. For instance,
if the user wishes to add up 2+2, he/she would directly enter the numbers
via the keyboard to the CPU and they are placed on the ALU before they
are added up. The ALU is made up of two main parts:
	
a. The arithmetic part which deals with adding up only numbers
b. The logic part which deals with letters, words, and images.


Definition #2
--------------
This is where the CPU performs the arithmetic and logic operations. 
Every task that your computer carries out is completed here. Even typing 
into a word processor involves adding binary digits to the file, and then 
calculating which pixels on the screen should change so that you can see the 
characters. The ALU’s operations fall into two parts:

a. the arithmetic part, which deals with calculations, eg 1 + 2 = 3
b. the logic part, which deals with any logical comparisons, eg 2>1

Note: One clock cycle per second = 1 Hertz (hz)
Clock speed is measured in Gigahertz(GHz) - about 1 billion
cycles per second!

1. It controls the way data moves around the CPU
2. It controls and monitors the flow of data between the 
CPU and other components such as input devices, memory, 
graphics card etc
3. It executes the instructions provided by the program

Regulate and control timing signals for the computer, which means 
it is responsible for instigating what is called the 
machine cycle, or the pulse of information packets, to make sure 
information packets are sent out regularly (every few milliseconds)

washing	machines 
microwaves 
televisions 
set-top boxes 
central heating systems 
cameras 
DVD players

Electronics began with the development of the transistor in the 1950s. Transistors are 
tiny electronic switches and amplifiers. Several thousand transistors can be put on a 
piece of silicon with a surface area of just one square mm.

A modern CPU that would fit in the palm of your hand can contain in excess of 2 billion 
transistors!

The program counter gives an address value in the memory of where 
the next instruction is.

The processor fetches the instruction value from this memory 
location.

Once the instruction has been fetched, it needs to be decoded and 
executed. For example, this could involve taking one value, putting 
it into the ALU, then taking a different value from a register and 
adding the two together.

Once this is complete, the processor _________________________________
_____________________________________________________________________

This cycle is repeated until the program ends.

#1. In the fetch stage, the ALU provides a pointer to the program
counter. The program counter then executes the instruction directly
by sending instructions via the data and address bus. 


#2. In the fetch stage, the program counter provides the memory
address of the next instruction. This is transferred through the 
address bus to the memory and the instruction is transferred to the
instruction register of the CPU through the data bus.