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 Processor  The 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) InputOutput Storage

CPUs: Different packages

CPUs: Things to notice  See 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 computer  Plugs into the ‘Motherboard’  The pins all plug into a socket  What is a motherboard?

Motherboards  We’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

Memory  We 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, speeds  RAM 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 like  Long, thin chips  Inserted in motherboard in rows

How RAM connect to motherboard  Notice the markings on the board?

Buses  We 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 BUSES  Like 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

Buses  However, 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 Bits  However, it is faster if we can send multiple bits at the same time  In PARALLEL

Buses: Multiple Bits  So parallel is faster  But, how do we send multiple bits at the same time?  MULTIPLE WIRES!

Buses: Multiple Bits  So:  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 Ports  We 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 Slots  Devices 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 Slots  With 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

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/Slots  An 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 Standards  Expansion 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 Bus/Slots  New 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 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

Ports  We’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?

Ports  How 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 Ports  Also very old  Faster 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 Ports  Specialized ports, used only for keyboards and mice  These devices don’t require much speed

A couple of other Ports  There 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

IDE  Normally, a computer has two ports  Each port can support two devices  SO, a maximum of 4 IDE hard drives/CD- ROMs/DVDs in a system

SCSI  SCSI is the last connection type we will talk about  Small Computer System Interface  Pronounced ‘scuzzy’  A very high speed connection  Uses a BUS  Can connect multiple devices to same port

SCSI  Used 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 PC  A good, step-by-step guide to installation of parts can be found at: system-05.html

Summary  You 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