Central Processing Unit (CPU)
Computer Service and Repair
Chapter 4
Ch 4
Instructions and Data
• The CPU is the computer’s brain
• In 1978 had 27,000 transistors now they have
over 2.5 billion
• CPU follows commands called instructions
• Instruction set is the set of basic commands all
CPUs follow
Add / subtract
Add one to / subtract one from
Get the next one, two, or, four bytes from
Put the next one, two, or
four byte at
Ch 4
Instructions and Data (cont’d)
• The Instruction Set is written in assembly
language – the lowest language level used to
program a computer (one step up from machine
• A compiler is a program that translates higher
level programs into machine language
• A register is a small pocket of memory in a CPU
used to temporarily store data that is being
– add number stored in register A to number stored in
register B place result in register C
Ch 4
CPU Operation
• CPU is in constant operation
– Refreshing memory
– Checking for communication from other devices
– Monitoring system power
– Performing other programmed duties
– Checking IRQ status
Ch 4
CPU Operation (Cont’d)
CPU Parts
• Bus Unit: network of circuitry that connects all off
the other major components together
• Instruction Cache: small temporary memory to
store incoming data and instructions
• Decode unit: decodes instructions
• Control Unit: controls overall operation of CPU
• Arithmetic logic unit (ALU) performs math functions
• Register unit: composed of many separate storage
units (register hold only one number or letter each)
Ch 4
CPU Operation (Cont’d)
Ch 4
CPU Operation (Cont’d)
• Not all business conducted on a PC requires the
use of a powerful CPU
– i.e. word processor
• Powerful CPU needs for graphic intense programs,
weather, or CAD programs
– i.e. 3D animation that requires redrawing every line of
image and calculations based on X,Y, & Z coordinates in
fractions of a second
• To save CPU time data not requiring manipulation
are now transferred directly to memory
• System clock send repetitive signal to all parts of
system to keep data transmissions in step
Ch 4
CPU Operation (Cont’d)
• CPU speed is measured in hertz Hz (cycles per
– Number of digital pulses per second
• Hertz is often referred to as frequency
• Speed became important as user interface
switched from text to GUI
• Each new generation of CPU operated on shorter
clock cycles (frequency)
Ch 4
Enhancing CPU Operation
• In addition to speed CPU have Improved:
• Local Bus: links devices directly to CPU
Video card slots
Referred to as system bus or front side bus
Shortened bus reduces inductive reactance
• Cache
– L1 cache is designed to run at same speed as CPU
– L1 allows CPU to quickly process data
– Two L1 Cache for each processor (one for instruction and one
for data)
– L1 memory is most costly to produce
– L1 is small on inexpensive processors
Ch 4
Enhancing CPU Operation (cont’d)
• L2 Cache: used to increase data from the
processor to other parts of the motherboard
– Originally separate from CPU mounted close on
– Moved in CPU with Pentium III
• L3 Cache:
– Originally added to mother board to speed when
L2 moved to CPU
– Now on CPU (shared between multi core CPUs)
Ch 4
Enhancing CPU Operation (cont’d)
• Floating Point Unit (FPU): a set of circuits in
the CPU that replace the math coprocessor
that was originally on the mother board
• Multiple Branch Prediction: guesses what
data the CPU will need next instead of waiting
for instructions to be issued (90% accurate)
• Superscalar execution: processing more than
one instruction at a time
Ch 4
Enhancing CPU Operation (cont’d)
• Dynamic Execution: CPU looks ahead if an
instruction can be carried out faster than the
instruction preceding it, it is moved ahead an
• Integrated Memory Controller: (IMC) Controls
data flow in front side bus to / from RAM
• Integrated Graphics Processing: (GPU)
enhances the ability of computer to produce
video and 3-D images
Ch 4
Enhancing CPU Operation (cont’d)
• Dual Independent Bus (DIB): Two separate bus
systems incorporated into the CPU
– One for Main Memory
– One for L2
– Both buses are use simultaneously
• Simultaneous Threading
– Thread is part of a software program that can be
executed independently
– Multi-core processors use two threads per core (quad
core runs 8X as fast as single core)
Ch 4
Enhancing CPU Operation (cont’d)
• Overclocking: running a CPU at frequencies higher than
Raises heat
Can / will damage CPU
CPU can accomplish more tasks in shorter time
Frequencies can be controlled by BIOS
• Turbo Boost Technology / Turbo CORE
Overclock CPU
Monitor temperature and energy use
Halts overclocking if temp gets to high
Intel provides free software (Intel Extreme Tuning Utility)
• Voids warranty
• Intel does not recommend
Ch 4
Process Description Features
• Reduced Instruction Set Computer (RISC): a CPU
Produced with fewer transistors and instruction
– Inexpensive but fast
– Software has carry modifications that allow for fewer
CPU computations
– Used in IPad, Iphone, Android, auto engine controls,
TVs, airplanes, robots, and servers
• Complex instruction set computer (CISC): A CPU
that processes complex mathematical formulas at
increased clock speed
Ch 4
Process Description Features (cont’d)
• MMX Processor: based on standard processor
with the addition of 57 commands.
– Enhances ability of CPU to support graphic technology
– Replaces functions of video and sound cards
– MMX could mean Multi-Media eXtensions, Mtrix Math
eXtensions, or as Intel claims nothing at all
• 32 bit vs 64 Bit (64 faster.)must have following:
– BIOS must support 64 bit technology
– 64 bit O/S
– 64 bit drivers
– Software written for 64 bit systems
Ch 4
Process Description Features (cont’d)
• Virtualization: a single physical CPU appear as
multiple processors to the system software and
the user.
– Allows multiple operating systems, users, and
application software simultaneously
– Normally applied to network servers
• System Management Mode: (SMM) Designed for
laptops to save energy
– Sleep
– Auto shut down
Ch 4
Process Description Features (cont’d)
• Cool ‘n’ Quiet (Process throttling): adjust
process speed and power consumption based
on temperature and software usage. Fan
speed may also be slowed
• Enhanced Intel SpeedStep Technology: When
laptop is plugged in Runs on 2.6 GHz applied
1.3 volts overall power consumed is 30 watts.
When on battery runs at 1.3 GHz and 1.2 volts
overall power consumed 20.8 watts
Ch 4
Process Description Features (cont’d)
• CPU operating voltage has dropped from 5
Volts to less than 1 volt
• Processor Size (physical) has not changed
significantly but the electronics have become
more compact
• Moore’s Law: (1965) Gordon Moore cofounder
of Intel predicted that computer calculating
power would double every year. He has been
pretty close (now takes about 18 months)
Ch 4
Processor Manufacturers
Three Biggest:
• Intel is the dominate manufacture of CPUs
since 1970’s
• AMD Intel’s biggest competitor.
• VIA Technologies is not as large as Intel or
AMD make processors and motherboards with
intel, AMD, and their own processors
Ch 4
Processor Evolution
• Intel Pentium (1993): front side bus
• Intel Pentium Xeon (Xeon 1998)
– network servers
– Hyper threading
– Not designed for entertainment
– Multiprocessors on each board ( blade servers)
– Used in web servers, cloud storage, and networks
• Intel Celeron (1999) general purpose computers
– Limited L1 and L2 counters high speed processor
results in less overall performance
Ch 4
Processor Evolution (cont’d)
• AMD Athlon 64 (2002) uses 32 and 64 bit processing
• AMD Opteron (2003)
for Network Servers
64 bit
Can process 256 TB
Usually runs between 800 MHz – 2.6 GHz
19 GB throughput
• AMD Sempron (2004)
– Low cost computers
– Two types (front bridge or HyperTranport)
Ch 4
Processor Evolution (cont’d)
AMD Athlon 64 X2 (2005) 64-bit dual core
AMD Athlon 64 FX (2006) introduced new socket
Intel Core Solo (2006) designed for laptops
Intel Dual Core (2006) Intel’s first dual core
Intel Dual Core 2 Duo (2006)Dual core, front bus,
variable L2
• Intel Core 2 Extreme (2007) gaming, 8MB L2
• Intel Core 2 Extreme Quad (2007) four processors
Ch 4
Processor Evolution (cont’d)
• Intel Core i3 (2011) minimal computing power for
devices that use the cloud
• Intel Core i5 (2011) intermediate processor does not
have Hyper-Threading good for average computer
systems with limited multi-media editing capabilities
• Intel Core i7 (2011)High Performance CPU
Turbo boost technology
Larges L3 Cache
Two types i7 & I7 Extreme (better graphics)
Ch 4
Processor Evolution (cont’d)
• Intel Atom: Specialized for low power consumption and low
– 32 and 64 bit
– Single and dual core
– Netbooks, tablets, smart phones
• AMD FX: Best AMD to Date
– 4,6,or 8 core
– 3-D graphics
– Designed for over clocking
– First CPU with 8 cores
• AMD A-series
– A4, A6, A8, and A10 similar to Intel i3, i5, i7
• AMD and Intel are too similar to say one is better than the other
must test specific software used to determine best for your use
Ch 4
Processor Affinity
• Processor Affinity is the ability to select the
number of cores to apply to a software
– System and Software must be designed to operate
in the multi core environment
– Software / system may lockup if mismatched
– Deselect any number of processors from CPU 0 to
CPU 7 to run the software application in the Task
Manager by selecting Processor Affinity
Ch 4
Processor Sockets
• Processor Sockets vary according into the number
of electrical connections.
• AMD and Intel are not interchangable
• AMD – Land Grid Array (LGA) Lands are small Flat
• Intel – Pin Grid Array (PGA) connectors are pins
• Originally techs pushed CPUs into Socket
– Lands and pins could be damages easily
• Zero Insertion Force Socket (ZIF) has one or two
levers the clamp onto pins or lands
Ch 4
Processor Performance
• CPU is not the only thing that affect system speed
• Download and Use a CPU analyzer
CPU-Z is free
Download from Cupid
Will identify CPU
L1 and L2 size
Socket type
Core and bus Speed
Ch 4
Questions to ask before Upgrading
What are you trying to achieve by upgrading CPU
Is the upgrade CPU compatible
Will Chip set and BIOS support the upgrade
Does the motherboard bus speed or chipset rather
than the CPU limit the increase in speed
• Does the chipset support desired features of the new
CPU such as 3-D tech
• Note:
– Cables / Modems affect download speed
– If main function is typing new CPU little effect
– If gaming new CPU May help is motherboard and chipset
support it
Ch 4
Installing a Processor
Remove cooling Device
Release locking lever(s)
Lift out CPU
Align pins (lands) to socket
Gently drop CPU into socket
Close locking levers
Reinstall cooling device
Ch 4
Installing a Processor
Ch 4
Cooling the Processor
• Electronic integrated circuits start to break down
at 160 degrees F
• Three Type of Cooling
– Simple heat sink and fan (most common)
• Heat sink paste
– Heat pipe cooling system (high performance)
• Hollow tubes with liquid that vaporizes and condenses at the
heat sink and returns to CPU by capillary action
– Liquid Cooling System (very high performance)
• Liquid is pumped rom CPU to a small radiator and back to CPU
(Most Expensive)
Ch 4
Heat Sink and Fan
Ch 4
Heat Pipe Cooling System
Ch 4
Liquid Cooling System
Ch 4
End of Chapter 4
Ch 4