boom

1. Inside The CPU
The Von Neumann Architecture
WACAYZ BOQORE
Department of Telecommunication Engineering
EELO University
Chapter 3

2. What’s inside the system unit?
• Motherboard (main-board)- Large printed circuit board with
thousands of electrical circuits
• Power supply- Transforms alternating current (AC) from wall outlets
to direct current (DC) needed by the computer
• Cooling fan- Keeps the system unit cool
• Internal Speaker- Used for beeps when error is encountered
• Drive bays- Housing for the computer’s hard drive, floppy drive and
CD-ROM / DVD-ROM drives

3. What’s on the Motherboard?
• System clock- Synchronizes the computer’s internal activities
• Microprocessor (CPU)- Central processing unit interprets and carries
out instructions given by software
• Memory- Enables the computer to retain information
• Chipset- A collection of chips that provide the switching circuitry
needed to move data
• Input/Output buses- Pathways that allow the microprocessor to
communicate with input and output devices

4. The CPU
• The CPU (Central Processing Unit) is the ‘brains’ of the computer.
• The purpose of the CPU is to carry out program instructions (each
CPU type is designed to understand a specific group of instructions,
the instruction set).
• On personal computers and small workstations, the CPU is housed in
a single chip
called a microprocessor.
A typical modern CPU
design showing the
pins that connect it
to the motherboard

5. What are the components of a typical CPU?
There are huge variations in CPU designs but most will share the following key
components:
• An electronic clock
• The control unit
• An instruction unit which consists of:
• The arithmetic logic unit (ALU)
• The floating point unit (FPU
• Various registers such as the accumulator.
• Various buses
• The bus management unit
• Registers
• Cache

6. Typical CPU Components – The Clock
• An electronic clock regulates the rate at which the CPU runs and
synchronizes all the various computer components.
• The higher the clock frequency, the more instructions the CPU can
execute per second.
• The speed of the clock (and therefore the speed of the CPU) is
measured in Megahertz (MHz).

7. Typical CPU Components – The Control Unit
• The control unit performs the tasks of:
Fetching instructions from memory
Decoding the instructions
Managing the execution of instructions and the storing of the results
• It does this mainly by controlling the links between the other components of the
CPU.
• It also contains various things such as:
• Sequencing Logic
• Control Unit , Registers and Decoders
• Control Memory

8. Typical CPU Components – The INSTRUCTION Unit
• An instruction unit consists of:
• The arithmetic logic unit (ALU) which executes basic arithmetic
and logical operations on integer data that it is linked to. Examples
of such operations include:
• Integer arithmetic operations (addition, subtraction)
• Logic operations (AND, NOT, OR, XOR)
• The floating point unit (FPU) which performs math functions on
floating point numbers (non-integer numbers).
• Various registers such as the accumulator that are used while
instructions are being executed.

9. Typical CPU Components – Buses
• Buses are sets of tiny parallel wires that carry data between CPU
components and between the CPU and external devices and RAM.
The three main bus types are:
• address buses - used to set which memory address a CPU component is
linked to for a read/write operation.
• data buses - used to exchange the data between a memory address and the
CPU when a read/write operation is carried out.
• control buses - used to transfer command codes and return status signals
between components of the CPU and external devices.
• The bus management unit manages the transfer of data along the
external bus connections, including the links to RAM.

10. Typical CPU Components – Register
• A register is a discrete memory location within the CPU designed to hold temporary data
and instructions, since it takes time to bring data from memory while you performing
calculations.
• Special purpose registers:
• Accumulator (ACC): stores the results of calculations made by the ALU.
• Program Counter (PC): keeps track of the memory location for the next instruction to be
deal with. The program counter then will passes this next address to the memory
address register.
• Memory Address Register (MAR): stores the memory location for data or instructions
that needs to be fetched from memory or stored into memory.
• Memory Data Register (MDR): a register that is used to store any data or instruction
fetched from memory or data that is to be transferred to and stored in memory.
• Current Instruction Register (CIR): Register that stores the most recently fetched
instruction while it is waiting to be decoded and executed.

11. Typical CPU Components – Cache
• Memory cache (L1, L2, or L3)
• Holds anticipated data and instructions needed by CU
• Improves performance
• Static RAM (SRAM)
• Holds data as long as power on
• Lets processor bypass slower dynamic RAM (DRAM)

12. What are the types of CPUs?
Advanced Micro Devices
(AMD)
Cyrix
Motorola (Apple)
Pentium IV
Pentium MMX
Pentium III
Two major processor manufacturers
Intel and AMD

13. Intel Processors

14. AMD Processors

15. Intel Processors (cont’d.)

16. The FDE Cycle
How it goes

17. Fetch-Decode-Execute Cycle
• Programs are stored in memory as machine language instructions, in
binary.
• The task of the control unit is to execute programs by repeatedly
carrying out the fetch-decode-execute cycle.

18. Fetch
• Step 1- the program counter copies the address of the next instruction it
contains into the memory address register(MAR).
• Step2- the control unit loads the address to be used on to the address bus.
• Step 3- the control unit triggers a read signal that causes main memory or
RAM to place the instruction being asked for on to the data bus.
• Step4- the instruction on the data bus is loaded into the memory data
register(MDR).
• Step5- the memory data register copies the instruction into the instruction
register(CIR).
• Step6- the program counter can now reset to point to the next instruction.
• Note the PC may be changed at a different point in the FDE cycle.

19. Decode
• The control unit examines the instruction in the current instruction
register(CIR) and decode it. It does this by issuing a series of micro-
instruction.
• For example, the instruction might say Add.
• The decode unit understands what this means and gets the system
ready to carry that instruction out.
• Every CPU has an instruction set that defines what the decoder
understand as legitimate commands.
• All software eventually ends up as a set of commands from within the
instruction set.

20. Execute, Then Repeat
• Execute the instruction with in the instruction register is carried out
(executed) by the CPU.
• This process may use the accumulator, the ALU as well as taking data
values from memory depending on the exact nature of the
instruction.
• Repeat/reset- the FDE cycle starts again.
• This is the Fetch-Decode-Execute cycle that is present in every
sequential processing computer.

21. EXECUTION CYCLE: BY THE CU/ALU
• Execution cycles vary, depending on the op code.
• Eg: load register R03 with contents of memory cell 47: Just for culture: The CU
causes the load to occur.
• CU activates ALU circuitry, which performs the actual Op Code. EG: MUL, ADD,
DIV, …
E.G: an arithmetic operation: ADD
1. LOAD
• Data copied from memory to ALU register.
2. ADD
• Data values are added in ALU adder circuitry.
3. COPY
• Result stored in ALU accumulator.
4. STORE
• Result copied from ALU to memory.
12

22. Cooling Methods and Devices
• Processor overheating results
• Processor damage and instability
• Entire system overheating results
• Sensitive electronic component damage
• Devices used to keep system cool
• CPU fans, case fans, coolers, heat sinks, liquid cooling systems, dust-
preventing tools
• Important
• Keep processor and entire system cool

23. Coolers, Fans, and Heat Sinks
• Cooler sits on top of processor
• Maintains 90–110 degrees F temperature
• Consists of fan, heat sink
• Made of aluminum, copper, combination of both
• Bracketed to motherboard using wire, plastic clip
• Thermal compound eliminates air pockets
• Fan power cord connects to 4-pin fan header
Figure 6-9 A cooler sits on top of a processor to help keep it cool

24. Figure 6-12 A cooler fan gets its power from a 4-pin PWM
header on the motherboard
Figure 6-11 Thermal compound is already stuck to
the bottom of this cooler that was purchased
boxed with the processor

25. Dealing with Dust
• Dust insulates PC parts like a blanket
• Causes overheating
• Dust inside fans
• Jams fans, causing overheated system
• Ridding PC of dust
• Make it a part of regular preventive maintenance
• Tools
• Antistatic vacuum
• Compressed air

26. CPU characteristics vs. performance
• Data bus width- The number of pathways within the CPU that
transfers data (8, 16, 32, 64)
• Word size- The maximum number of bits of data that the CPU can
process at a time (8 bits, 16 bits, 32 bits, 64 bits)
Specifications:
Clock Speed: 1.0 GHz
System / Front Side Bus Speed: 133 MHz
Level 1 Cache: 16K Instruction + 16K data
Level 2 Cache: 256 KB

27. CPU characteristics vs. performance
Clock speed:
• Although it might seem that a computer is
carrying out many tasks simultaneously, the
CPU is actually only ever processing one
instruction at a time and is constantly
switching between programs (sets of instructions).
• The speed that the processor executes instructions is controlled by the clock
speed and is measured in MHz (megahertz).
• The CPU requires a fixed number of clock cycles to perform each instruction.
Summary:
• The higher the clock speed, the more instructions the CPU can execute per
second, resulting in a faster running computer system.

28. CPU characteristics vs. performance
• Overclocking
• Running motherboard or processor at higher speed than
manufacturer suggests
• Override default frequencies
• Change setting in BIOS setup
• Disadvantages
• Overheating
• Voids most warranties
• Not recommended in business environment

29. CPU characteristics vs. performance
Cache size:
• Cache memory is a small amount of very fast
memory that is built into the CPU. Blocks of
instructions and data that are in use by the CPU
are copied from RAM into cache memory, along
with the associated memory addresses.
• If the CPU needs to access a memory address it
first checks the cache memory to see if there is a
match. If there is then it access the contents of
the cache version.
Summary:
A CPU with a larger cache memory and more levels of cache memory will
have a higher performance than one without cache memory.

30. CPU characteristics vs. performance
Number of Cores:
• A multi-core processor is a single computing component with two or more
independent actual processors (called "cores").
• A dual-core processor contains two cores and a quad-core processor contains
four cores. Each core can process instructions independently of the other cores.
• The biggest performance gain when using a multi-core processor is when the
software has been specifically written to run on multiple cores.
Summary:
• A multi-core CPU will have a higher performance than a single-core CPU with the
same clock speed.

31. CPU characteristics vs. performance
• Three methods to improve performance
• Multiprocessing
• Processor contains more than one ALU
• Multiple processors
• Installing more than one processor on a motherboard
• Multi-core processing
• Processor housing contains two or more cores operating at
same frequency, independently of each other
• Dual core, triple core, quad core, octo core

32. Selecting and Installing a Processor
• PC repair technician tasks
• Assemble PC from parts
• Exchange faulty processor
• Add a processor
• Upgrade existing processor
• Must know how to:
• Match processor to system
• Install processor on motherboard

33. Select a Processor to Match System Needs
• First requirement
• Select processor motherboard is designed to support
• Select best processor meeting general system requirements and user
needs
• May have to sacrifice performance for cost
• General steps
• Read motherboard documentation
• Select processor by comparing processors board supports
• Select cooler assembly

34. Install a Processor
• Installing an Intel processor in socket 1366
• 1. Read and follow all directions
• 2. Use a ground bracelet
• 3. Open the socket
• 4. Lift socket load plate
• 5. Remove socket protective cover
• 6. Remove processor protective cover
• 7. Lower processor straight down into the socket
• 8. Verify processor aligned correctly in the socket
• 9. Return lever to its locked position

35. • Coming up next: Chapter 4
The Memory Unit
Thank You
COME TO CLASS .. ASK QUESTIONS
READ CHAPTERS !