Describe the purpose of the CPU Understand how ROM, RAM, I/O,
storage link to CPU Explain performance of CPU looking at clock
speed, cores & cache
Slide 2
The CPU (Central Processing Unit) is hardware that executes
programs and manages the rest of the computer system. It sits
underneath the heat sink on the motherboard and is made up of
millions of electrical switches called transistors. All data is
stored within a computer as electronic signals in micro-circuits.
There are only 2 types of signal on or off. A micro-circuit can
either carry an electrical signal or not. This will lead to our
discussion of binary later in the course. The CPU is often known as
the brains of the computer and its purpose is to process data. It
does this by performing functions such as calculating, decision
making and moving data around. Our computers would not work if not
for the CPU, similar to us not functioning without our brain! Think
of all the tasks our computer does. Write a list of 10 jobs. Eg.
Perform a function on a spreadsheet
Slide 3
Processor speed has doubled over time while a second processor
has resulted in the phrase dual-core which is a double processor
doubling the speed. It doesnt stop there, quad-core, hexa-core and
octa-core offer the next steps to power our machines even faster.
Software running on our systems have to be designed to take full
advantage of all these new progressions. Current mobile devices
will carry mobile processors; small versions without fans to keep
it cool. the CPU will deal with all the data processing, without it
none of your tasks will be performed. The first CPU chip was
invented in 1971 a 4 bit processor designed for a calculator! This
is where our story starts
Slide 4
You input information and commands using the mouse and
keyboard. You see/hear the results on the output devices- screen
and speakers The CPU ("processor") is the working brain of the
computer, that does all the processing and computation The memory
("RAM") is where the CPU keeps information it is working with (the
information in the RAM is lost when the computer is switched off)
Storage (e.g. hard-disks, USB data sticks) is where the computer
keeps information for longer periods (not lost when the computer is
off)
Slide 5
The CPU consists of 3 major components: The Arithmetic and
Logic Unit (ALU) The Memory Unit The Control Unit (CU) The ALU
carries out mathematical tasks rapidly, performs calculations and
logic operations in binary form 1/0 on data from the memory unit.
The ALU transforms the digital data and outputs the resulting
value. The Memory Unit consists of a small number of memory
registers which will store items of data and send them to the ALU
for processing. The result of the processing will be copied back to
the memory unit for storage. The CU is in charge of processing. It
interprets the software instruction and sends the right data and
operation to the ALU. It accepts the result of the processing from
the ALU and sends it back to the memory unit. The CU will keep
track of the sequence of instructions and the location of each item
of data and software instruction in the memory unit.
Slide 6
It runs a computer program What is a program? Program : the
sequence of instructions stored in memory required to solve a
specified problem Computer architecture:
Slide 7
Slide 8
Slide 9
Fetch : read instruction from cook book. Decode : understand
instruction and get ingredients from store Execute : crack egg into
bowl.
Slide 10
The CPU will typically perform the following execution cycle:
The CU fetches a single instruction and data from the main memory
The instruction is decoded. The ALU executes the instruction The
ALU sends the result of the processing back to the control unit
this is stored in the memory unit.
Slide 11
Just how does the CPU interact with the rest of the system? A
bus or a cable (a collection of fine wires) The System Bus is a
major component of a computer: Data Bus: Carries the data that
needs processing Address Bus: Determines where data should be sent
Control Bus: Determines data processing
Slide 12
ROM & RAM are memory areas that are closely linked to the
CPU. RAM is the type of memory used in the computers main memory.
RAM is the active memory of the computer. The contents of all open
software applications and data files are held in RAM. So when a
program is running it has to be loaded from the hard disk into the
main memory so the processor can access the instructions. RAM acts
as temporary storage for programs and data just while it is
running. This makes it volatile. Once the program has finished and
closed it is no longer main memory. ROM is Read Only Memory you can
not write over the contents once it has been created. This makes it
non-volatile. More on ROM & RAM later in the course
Slide 13
The power and speed of a computer is limited by the speed with
which the computer can carry out the fetch-execute cycle. Computers
can only process one instruction at a time. If you are running many
programmes eg. Surfing the net, working on an essay, listening to
music and sending an e-mail all at the same time (multi-tasking) it
may seem that the computer is processing all these tasks
simultaneously. In reality it is handling one instruction at a time
but it does it rapidly! The amount of time the CPU has to process
each instruction is controlled by a quartz clock, with every tick
the CPU is able to process one piece of data or execute one
instruction. The CPU clock speed is measured in cycles per second.
1 cycle peer second is known as 1 Hertz. A computer running at 1GHz
can carry out a thousand million instructions per second. So the
speed of the clock determines the basic performance of the CPU the
faster it goes, the more powerful the computer. If the CPU has more
than one core, it can execute more than one instruction.
Slide 14
Cache memory is memory that can be accessed rapidly by the
processor. It holds a copy of the data that is stored elsewhere. If
the processor has to access main memory less often it can work
faster so the CPU performs better. The data that the computer needs
right away is taken from storage before processing begins and kept
in cache memory while it is in use. There are several types of
cache: The memory register is very small cache, it holds data for
immediate use. L1 cache is small, fast and expensive L2 cache is
larger but slower In programming a cache library can be used for
storing database queries for later use.
Slide 15
CPUThe central processing unit of a computer. Hardware that
executes programs and manages the system ALUThe arithmetic and
logic unit. Part of the CPU where data transformation occurs. It
operates electronically. Fetch-Execute Cycle A single operation of
the CPU: a stored instruction is taken from memory, carried out and
the resulting value stored to memory. Dual-Core Processor A CPU
with 2 processing components to speed up tasks Cache MemoryActs as
a buffer between main memory and the CPU fast memory ROMRead Only
Memory Not Volatile RAMRandom Access Memory - Volatile
Slide 16
Fill in the blanks with the given words NAME:
______________