Week 10

CPU/Motherboard/Memory/Buses/Slots/Ports

We have a lot to cover!We will not go into great detail

Basics of operation of CPU, Motherboard, Buses

Survey of Slots and Ports Enough to tie our picture together

The ProcessorThe heart of the computer is the

processor CPU, for Central Processing Unit Very complicated beasts!

We will summarize its function

The CPU Performs all instructions in programs Processes information

Does all math, comparison, etc. Info goes in, info comes out!

The ALU (Arithmetic and Logic Unit) performs these tasks

Controls other devices in the system Includes a small amount of built-in memory

To store the data it is currently using ‘Registers’ and ‘Cache’

In the System

Processor

(CPU)Input Output

Storage

CPUs: Different packages

CPUs: Things to noticeSee all of the pins sticking out?These are the wires that connect it to

the outside world Wires means information in and out

How a CPU plugs into the computerPlugs into the

‘Motherboard’ The pins all plug

into a socketWhat is a

motherboard?

MotherboardsWe’ve talked about how all information

in a computer passes over ‘wires’ Electrical current!

There are lots of components to connect!

If we just used WIRES, it would look like spaghetti!

Motherboard Rather than dealing with spaghetti, a system

has been developed where one component contains ALL of the wiring Well, almost all…

The wiring is all done with printed circuits No wires dangling!

Every other component plugs into this component, to be connected to the others

Motherboard This component is the Motherboard (or

Mainboard) Motherboard provides wiring to connect

components All components plug into motherboard

Motherboard also controls things like timing Don’t worry too much about this

Motherboard

MemoryWe know that the computer needs

Memory Stores the programs and data currently in

use

RAM: Random Access Memory

RAM RAM comes in chips called DIMMS (now)

RAM works very simply… Every bit is represented by a CAPACITOR

A capacitor can store an electrical charge (sort of like a battery…)

Store a bit: Store the electrical charge (on or off) Read a bit: Test to see if there is a charge or not

Don’t worry about any more detail than that!

RAM comes in many sizes, speedsRAM keeps evolving, to become bigger

and faster Typical modules today are 128M, 256M,

512M There is a list of terms on page 107

Latest types DDR- Like SDRAM, but faster Rambus- Faster still, but expensive!

What RAM looks likeLong, thin chips Inserted in motherboard in rows

How RAM connect to motherboard

Notice the markings on the board?

BusesWe pause for a moment, and talk about

the wiring itself

We know that: Information is transferred over wires Much of the wiring is provided by the

motherboard

Buses Indeed, the wiring on the motherboard

transfers information Important channels (‘highways’) of

information are called BUSESLike a highway, multiple devices all

share the same bus There may be 10 devices on the bus, but

any two of them can use the bus to communicate

Buses: Multiple devices sharing the same lines

BusesHowever, we know that to transmit

USEFUL information, we need more than 1 bit!

Buses: Multiple Bits It is possible to send multiple bits over a

single wire Send them one at a time! In SERIAL

Buses: Multiple BitsHowever, it is faster if we can send

multiple bits at the same time In PARALLEL

Buses: Multiple BitsSo parallel is fasterBut, how do we send multiple bits at the

same time? MULTIPLE WIRES!

Buses: Multiple BitsSo:

Information needs to be passed as quickly as possible on the motherboard’s buses

Parallel is faster than serial Multiple wires are needed for parallel

Therefore, BUSES ARE MADE UP OF MULTIPLE WIRES

Buses: Multiple, Parallel Wires If you look at the motherboard, you can

see the buses They are the groups of lines that run in

parallel

Buses Data is passed around on the motherboard

using buses Components plug into the motherboard to

connect to other devices Therefore, components connect to the

buses! As we learn about other connectors, you will be

able to see that they all connect to a bus!

Slots/Ports/Etc.: Familiarity Required There is a great deal of information on

various expansion cards, ports, etc. You are not expected to memorize it all!

Read over for familiarity

What you will be expected to know: Only for types mentioned in the presentation

Name (acronym, not the full name) The degree to which it is used today What types of devices typically use the interface How fast it is (relative to other ports which can be used

for the same type of device)

Expansion Slots and PortsWe know that we can connect lots of

different devices to our computer

These items must connect to the motherboard somehow There are two primary methods: Expansion

Slots, and Ports

Expansion SlotsDevices may be either INTERNAL

(inside the ‘box’) or EXTERNAL Sometimes, we have a choice

E.g., Modems

Expansion slots are often used for INTERNAL devices

Expansion Slots In earlier readings (p. 14), you learned about

circuit boards Virtually all electronic devices use circuit boards

With an external device, you need to package up that circuit board, build a way for it to connect to the computer, etc. Expensive!

Expansion SlotsWith internal devices, we can avoid all

of this expense! Just provide a circuit board, with no

additional packaging This is called an EXPANSION BOARD

Plugs directly into the motherboard

An Example

An Example

Things to notice… They are normal circuit boards

Lots of components!

They each have a set of ‘pins’ which plugs into the slot These pins are the wires that connect it to the

motherboard Why so many pins?

They connect to a BUS on the motherboard Lots of lines for information

Other wires for controlling the board, etc.

Expansion Slots/Buses If you look on the motherboard, you will

see that there are ‘bus’ wires running to each of the expansion slots

Plugging a board in connects it to a bus The board can now communicate with the

motherboard, and other components!

Expansion Boards/SlotsAn expansion board plugs into an

expansion slot This is an example of an INTERFACE!

What do we know about interfaces? They have to match EXACTLY For this reason, they are often

standardized

Expansion Slot StandardsExpansion slots are standardized

To ensure that any manufacturer’s board will work with anyone else’s motherboard

There are a handful of standard interfaces that you need to know about

ISA Slots

ISA Slots…Are an older technology

(Supports 16 data bits) May not exist on newer PCs Slower than current technologies

Used for general internal peripherals Modems, sound cards, network boards,

etc., etc.

PCI Slots

PCI Slots

PCI Bus/SlotsNew technology

(32 data bits)Primary general-purpose slot for

modern PCs Use for modems, sound cards, network

boards, (sometimes) video, etc.Much faster than ISA

That’s why it replaced ISA!

AGP Slot

AGP Slot AGP stands for Accelerated Graphics Port Only used for VIDEO cards

Most common graphics interface today Normally, you only have 1 AGP slot on your

motherboard

Very, very fast Much faster than PCI Needs to be fast, to support games!

Slots on a Motherboard

Slots on another Motherboard

How do you tell the difference? You get to know them… Color can provide you a clue

PCI are normally white ISA are black There is only one AGP…

You normally know what type of card you have It will only fit one type of slot You can then tell what type of slot it is!

How can you tell what a board does?Usually, you can tell by the jacks (ports)

on the back of the board Headphone-type jacks-> sound card Telephone jack-> modem Network jack->network card Monitor(VGA) port->video card

PortsWe’ve discussed the role of expansion

slots Internal devices

However, sometimes devices are external Why, if it’s more expensive?

Convenience – portability, etc. Physical requirement – can you imaging using

an internal printer, or joystick?

PortsHow do external devices connect

They use cables The cables plug into the computer

They plug into PORTS!

So, a port is similar in idea to a slot, but it’s for external use

Ports If you want to see ports, look at the back of

your computer All of those sockets are ports

How do we make sense of them? Again, there are standards for ports

You’ll find plugs will only plug into ONE TYPE of socket Prevents you from inserting the plug in the wrong

socket

Serial Ports Also known as RS-232 Very simple, found on virtually every PC Very OLD! ‘Serial’, because the only have one wire to send data

Data is sent one bit after another Slow! Other wires for control, etc.

General purpose port Not used much now, because of speed Now, sometimes used for mice, PDAs, Digital Cameras, etc.

                                                                   

                                               

Parallel PortsAlso very oldFaster than serial ports

Instead of one wire for data, it has 8 wires, and sends 8 bits at a time (‘in parallel’)

Hence, more pins than serial! Other wires for control, etc.

Often called ‘Printer Ports’ Used mostly for printers, even today, and

sometimes scanners

USB Ports A much newer type of port

New devices support this type of port Much higher speed than serial, parallel General purpose port

There are devices of all kinds which can use USB Network adapters, joysticks, keyboards, scanners, digital cameras,

hard drives, etc., etc.!

USB stands for Universal Serial Bus Because it is a BUS, you can connect multiple devices to it

Using the same port

Supports lots of advanced features See your text for details

PS/2 PortsSpecialized ports, used only for

keyboards and miceThese devices don’t require much

speed

A couple of other PortsThere are two more types of

connections which we will talk about

They don’t strictly fit into either category Require a cable to be used But, often used for internal devices

IDE Connections IDE connections are used for hard

drives, CD-ROMs and DVDs Found in virtually every PC

Requires a cable A flat, ‘ribbon’ cable A cable can connect up to two devices

Only used INTERNALLY

IDE Ports- Notice the name?

IDE Cable

IDENormally, a computer has two portsEach port can support two devices

SO, a maximum of 4 IDE hard drives/CD-ROMs/DVDs in a system

SCSISCSI is the last connection type we will

talk about Small Computer System Interface Pronounced ‘scuzzy’

A very high speed connectionUses a BUS

Can connect multiple devices to same port

SCSIUsed for very high speed transfer

Higher-end hard drives Higher-end scanners Etc.

Drawback: Expensive Not normally found in a basic PC

Needs to be added on

SCSI: Many different connectors

Assembling a PCA good, step-by-step guide to

installation of parts can be found at:

http://www6.tomshardware.com/howto/01q1/010115/pcsystem-05.html

SummaryYou should have a broad understanding

of how the various components of a computer connect with each other How they plug in How the data is transferred