Transcript System memory

Chapter 2: The System Unit
Computing Fundamentals
Chapter 2: The System Unit
Learning Objectives:
• Recognize how data is processed
• Understand processors
• Understand memory types and functions
• Identify and use ports and buses
• Troubleshoot common system unit problems
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Computing Fundamentals
Understanding CPUs
• Every computer has at least one processor, also
called Central Processing Unit (CPU)
• The CPU contains millions of tiny transistors and
pathways that:
• take in data and instructions,
• process (calculate) the data according to the instruction,
and
• output the results of the calculations
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Computing Fundamentals
Understanding CPUs
• Every CPU includes the following components:
• Control Unit
• Manages the flow of data through the CPU
• Arithmetic Logic Unit (ALU)
• Does the actual processing
• Receives data and instructions and delivers a result
• Registers
• Holding areas for data and instructions
• Different registers, each with its own special purpose
• (e.g. for holding data, for holding instructions, for storing
logical states (yes/no) etc.)
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Computing Fundamentals
Physical Composition of a CPU
• A very thin sheet of semiconductor material (silicon)
with a complex array of tiny transistors and buses
• Semiconductor material does not affect the electrical
flow (electricity-neutral)
• Encased in a ceramic shell for its protection and
mounted on a small
circuit board
• The underside of the CPU
contains tiny pins or contacts
(metal dots)
• Each pin or dot is a separate
communication line, carrying a different piece of data
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Computing Fundamentals
Physical Composition of a CPU
• Most modern PC CPUs have multiple cores
• Completion of multiple tasks simultaneously
• Common numbers of cores are 2, 4, or 6
• e.g. most models of Intel i7 processor have four cores
• Core A set of the essential processor components that
work together (control unit, ALU, and registers) All
located on the same chip of the CPU
• Multiple cores allows parallel processing for greater
throughput
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Computing Fundamentals
Clock Cycle
• The CPU is capable of executing a function
with every tick of the system clock the
system clock (called a clock cycle).
• However, in practice, the CPU sometimes is idle
because there is a delay between the request
for data to be retrieved from memory and its
delivery.
• A delay caused by waiting for another
component to deliver data is called latency.
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Computing Fundamentals
Cache
• To help minimize latency, CPUs have caches.
• A cache is a small amount of very fast memory
located near (or within) the CPU.
• Data that the CPU has recently used, or is predicted to
need soon, is placed in the cache for temporary holding.
• That way, if the CPU calls
for the data, it’s more
readily available and
there is less delay.
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Computing Fundamentals
CPU Performance Factors
• The most obvious performance factor for a CPU is its
maximum speed, measured in billions of hertz, or
gigahertz (GHz).
• Hertz: One cycle per second, a measurement of activity
speed.
• A CPU’s word size also makes a difference.
• Word Size is the number of bits
that the CPU can accept as input
simultaneously, either 32bit
or 64bit.
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Computing Fundamentals
CPU Performance Factors
• Because modern CPUs have many technology
improvements in them, speed and word size alone
do not form a reliable benchmark of a CPU’s
capability.
• Benchmark A consistent measurement of performance.
• Another way to look at performance is how many
instructions per second the CPU can process.
• Instructions per second: A measurement of a CPU’s
throughput capability, taking into consideration factors
such as number of cores and latency.
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Computing Fundamentals
Understanding Memory
• Static (non-volatile): Memory that retains its data
without electricity being constantly applied.
• Dynamic (volatile): Memory that must be constantly
refreshed.
• It stores data until the computer is turned off
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Computing Fundamentals
Understanding Memory
• Random Access Memory (RAM): that can have its
values changed freely, an unlimited number of times.
• Read-Only Memory (ROM) In general, memory that
cannot be rewritten. However, there are exceptions to
that in newer types of ROM.
• Electrically Erasable Programmable ROM (EEPROM):
ROM that can be erased and reprogrammed with
electricity.
In other words:
 RAM = rewriteable
 ROM = not rewriteable (with exceptions)
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Computing Fundamentals
How Computers Use Memory
• Computers use different types of memory in various
ways:
1. System memory (main memory) Such as the RAM
installed in PC’s motherboard.
• Systems Memory is dynamic RAM (DRAM).
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Computing Fundamentals
Understanding System Memory
• Each computer has a certain amount of system
memory:
•
•
•
•
called also RAM or main memory
Is a dynamic RAM (DRAM)
Loses content if not constantly electrically refreshed
The more memory , the more applications and file that
can be opened at once.
• Virtual memory is simulated memory by dataswapping on/off the hard drive
• Used as extension to main memory
• Paging file (called also swap file) is the area of the
hard drive dedicated for virtual memory
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Computing Fundamentals
How Computers Use Memory
2. Component memory (printers, display adapters):
Many components have a small amount of
memory built in for their own use.
• Example: A printer might have RAM (typically DRAM)
that holds information on page being printed.
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Computing Fundamentals
How Computers Use Memory
3. ROM-BIOS (EEPROM chip): contains low-level startup
instruction for the hardware.
• use a type of EEPROM to store data.
• Not rewritable except with a special utility program.
4. CPU caches: a type of static RAM.
5. USB flash drives, Memory cards, Solid-state hard
drives:
• use a type of EEPROM to store data, called flash memory
• Data can be written and rewritten multiple times
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Computing Fundamentals
Memory’s Physical Form
• System memory comes mounted on small rectangular
circuit, called Dual inline memory modules (DIMMs).
• Circuit boards fit into memory slots on motherboard
• Different types and speeds of DIMMs.
• Capacity ranges from 2, 4 or 8 GB of RAM.
• Small-outline DIMMs (SO-DIMMs) for portables such
notebooks.
Some DIMMs have a metal plate covering the chips for better heat
dissipation.
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Computing Fundamentals
Memory’s Physical Form
Most common type of DRAM is known as SDRAM.
• Synchronous DRAM (SDRAM) synchronizes with
the system bus speed (operates at the speed of the
system clock). Two types
• Single data rate SDRAM (SDR SDRAM)
• Performs one action per clock tick.
• Double data rate (DDR SDRAM)
• Performs two action per clock tick
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Computing Fundamentals
Understanding Motherboards
• Motherboard: large circuit board inside the computer
• Capabilities dictated by chipset.
• Chipset: The controller chip on a circuit board.
• Form factor: size and shape of motherboard.
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Computing Fundamentals
Understanding Motherboards
• Expansion Slot: A slot in the motherboard into which
an expansion card (a small circuit board) can be
installed.
• Expansion Card A small circuit board that fits into a slot
on the motherboard to add functionality.
Expansion slots
Expansion card
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Computing Fundamentals
Understanding Motherboards
• PCI (Peripheral Component Interface):
• A motherboard slot that accepts PCI expansion boards.
• PCI is considered a legacy interface (mostly obsolete)
• PCI Express (PCIe):
• A new and updated version of the PCI motherboard slot.
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Computing Fundamentals
Understanding Motherboards
• ExpressCard slot in notebooks
• adds a capability to the system, such as wireless
networking
• PCI Express Mini Card socket in notebooks
• small circuit board that can be installed in a notebook
PC’s PCI Express Mini expansion bay to add a new
capability
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Computing Fundamentals
Built-In Components
• Graphics Ports:
• Digital Visual Interface (DVI): A digital port for
connecting a monitor to a PC.
• Video Graphics Array (VGA): An analog port for
connecting a monitor to a PC.
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Computing Fundamentals
Built-In Components
• Speakers/Headphones
• 3.5 mm
• Ethernet networking
• RJ-45 jack
• Resembles a wide telephone plug
• Universal Serial Bus (USB)
• general-purpose port for connecting
external devices to a PC.
• USB 1.1, 2.0, 3.0 speeds
• FireWire (IEEE 1394)
• for high-speed connection, such as
some external hard drives and video
cameras.
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Computing Fundamentals
Different USB Types *
USB 3.1 Type C
First Reversible USB Port
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Computing Fundamentals
Built-In Components (Legacy)
• PS/2
• Used for older keyboards
and mice
• Parallel Port
• Used for older printers
• Serial Port
• Used only for very old
components (mice, modems)
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Computing Fundamentals
Drive Connectors
• Parallel ATA (PATA)
• Older hard disk drives
• Older CD and DVD drives
• Serial ATA (SATA)
• Newer hard disk drives
• Newer CD and DVD drives
• Solid-state hard drives
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Computing Fundamentals
Understanding Power Supplies
• Power supply has two functions:
• Converts AC (Alternating Current) to DC direct current.
• Decreases the voltage to the appropriate levels for the
devices it powers
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Computing Fundamentals
Understanding Power Supplies
A power
connector for a
Serial ATA
(SATA) hard
drive..
Fig. This connector runs from the power supply to the
motherboard, delivering all the different voltages that
devices that connect directly into the motherboard
might need.
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Computing Fundamentals
Notebook Power Supply
• Transformer block (brick): A thick block built into a
power cable for a device that handles the conversion of AC
power to DC and decreases the voltage to the level needed.
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Computing Fundamentals
Key Terms
active heat sink
benchmark
cache
Central Processing Unit (CPU)
chipset
CMOS setup
core
Digital Visual Interface (DVI)
double data rate (DDR)
dual inline memory module
(DIMM)
dynamic memory
Electrically Erasable
Programmable ROM
(EEPROM)
expansion cards
expansion slots
ExpressCard
form factor
gigahertz (GHz)
hard reset
heat sink
hertz
IEEE 1394A
instructions per second
latency
machine cycle
memory address
motherboard
overclock
paging file
Parallel ATA
parallel port
PCI Express (PCIe)
PCI Express Mini Card
Peripheral Component
Interface (PCI)
POST card
power supply
power-on self test (POST)
PS/2
Random Access Memory
(RAM)
Read-Only Memory (ROM)
RJ-45 jack
semiconductor
Serial ATA
serial port
single data rate (SDR)
soft reset
static memory
swap file
synchronous dynamic RAM
(SDRAM)
system clock
system memory
transformer block
Universal Serial Bus (USB)
Video Graphics Adapter
(VGA)
virtual memory
word size
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Computing Fundamentals
Summary
• 1 . What are the three basic components inside a
CPU?
• 2 . What are the four steps of the machine cycle, and
how do the parts you named in #1 fit into it?
• 3 . How do the L1, L2, and L3 caches improve CPU
performance?
• 4 . What is the difference between static and
dynamic memory?
• 5 . What are four ways in which one motherboard
may differ from another?
• 6 . Why does a power supply have different colored
wires?
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