CSIT 301 (Blum)1 Basic Hardware Overview (Continued)

CSIT 301 (Blum)2 In addition to power, hard-drives will have a data connection — either the older PATA Parallel Advanced Technology Attachment or the newer SATA Serial Advanced Technology Attachment

CSIT 301 (Blum)3 Floppy Disk Drive A storage medium that can be taken out of the case is said to be removable. (Some hard drives are removable.) The earliest storage in PCs was a removable magnetic medium known as the floppy disk. In the early to mid-80’s a standard computer had a dual floppy drive, the drives were designated A and B – leaving the hard drive when it became standard with the letter C. In addition to a power connector, a floppy drive would have a “ribbon cable” for data “a cable with a twist”

Shrinking Early on, floppy disks shrunk in size and gained in capacity but this stopped at 3-1/2 inch floppy disk with 1.44 MB of storage that is standard today. –But it is becoming standard to not have a floppy drive. CSIT 301 (Blum)4

5 CD ROM Drive CDs (Compact Disks) are an optical medium of storage that has become standard in PCs. A standard CD has about a thousand times the capacity of a floppy disk. Originally CDs were Read Only (CD-ROM), written by the manufacturer and useful as a software delivery system. As the amount of data users wanted to be portable grew, a recordable CD (CD-R) filled the void. But it had the limitation of being Write Once. Finally the rewritable CDs (CD-RW) became available. DVDs are similar to CDs but have higher capacity. Blu-ray

CSIT 301 (Blum)6 Keyboard Early computers inputting was done by plugging wires in boards or flipping switches or paper tape or punch cards. But the keyboard made data entry user friendly. PCs have always had generic connectors to plug in devices so that users could adapt them to various purposes, but the keyboard is so standard it soon had a designated connector and controller on the motherboard. –But more recently the keyboard has gone back to a generic port – namely the USB, Universal Serial Bus.

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8 Mouse The mouse was not a standard input device in early PCs. (They were initially frowned upon by people who considered themselves serious computer users.) But the user friendly graphical user interface (GUI) approach made using a computer more palatable to most users, and it soon became standard with its own designated connector. –Again the trend for devices becoming standard and having designated connectors has changed recently with the introduction of the USB (universal serial bus) and USB keyboards and USB mice.

CSIT 301 (Blum)9 Displays The earliest display devices were lights or light-emitting diodes (LEDs). However, any significant amount of binary output is difficult to read. The monitor was an early standard output device. Early monitors were monochrome Cathode Ray Tubes (CRTs) – the same basic technology as television (of the time).

CSIT 301 (Blum)10 CRTs A stream of electrons (a cathode ray) is aimed toward the screen which is coated with various phosphors; the electrons transfer their energy to the phosphors which then glow. There are phosphors for red and green and blue which can be combined to make all other colors. An individual speck is known as a pixel and the number of pixels determines the screen’s resolution.

CSIT 301 (Blum)11 LCDs CRT’s are OK for desktop computers, but laptops require something smaller and lighter; they need “flat panel displays.” A common flat panel display is the liquid-crystal display (LCD). Liquid crystals are molecules said to be in a state between liquid and solid. Their optical properties are affected by electric current or fields, hence their use as displays: watches, laptop screens, etc. Flat panels are replacing CRTs even on the desktop.

CSIT 301 (Blum)12 Expansion Cards In order to make PCs customizable, they have expansion slots – places where extra circuit boards called expansion cards can be added. The video card – extra circuitry needed to interface with the monitor – added to the capability of PCs.

PCI slot, PCI card CSIT 301 (Blum)13 PCI, Peripheral Component Interconnect, is a card, a slot, a bus, and a set of standards. These standards include Plug- N-Play.

CSIT 301 (Blum)14 NIC PCs were initially stand-alone devices. But networking proved to be important and then crucial. The PC’s expansion slots allowed a user to add a Network Interface Card (NIC) to allow the computer to exchange information with other computers. –But now this circuitry is often right on the motherboard rather than placed on an expansion card.

Wireless NIC A Wireless NIC or WNIC Has an antenna and uses electromagnetic waves (somewhat like radio or non-cable television) to communicate information. Many use a PCI slot. CSIT 301 (Blum)15

CSIT 301 (Blum)16 Ports Some history … In addition to expansion slots which allowed one to add circuitry to interface with peripherals, older PCs also had two standard interface paradigms that if a device could use these, additional circuitry was not needed. The device could just be plugged in. These places to plug theses devices are called ports and the two standards developed are serial connection and parallel connection.

CSIT 301 (Blum)17 Serial Communication A serial connection sends information over the line one bit at a time. It is a simple way to send information in or out of the computer, but originally was not as fast as other ways the computer can communicate. Serial connections are typically used for devices such as mice and modems.

CSIT 301 (Blum)18 DB Connector While serial data flows one bit at a time and can flow along a single wire. There’s more to communication than just flow of information. The two devices must agree to communicate, so there are additional wires needed. A generic serial connector is the DB connector. (DB – databus).

CSIT 301 (Blum)19 Serial Port The serial port is used along with a local communication standard that transmits 1 bit at a time. It is typically used for (external) modems but sometimes used for digital cameras and other devices. The standard was used for keyboard and mouse but they usually have special, designated connectors (unless they’re USB). Serial DB9 connectors

CSIT 301 (Blum)20 DIN connector A DIN connector is one that meets the DIN standards. DIN stands for Deutsches Insitut für Normung eV, the German version of ANSI, a organization that determines standards. On PCs DIN connectors are often used for keyboard and mouse. They may also been seen on routers and switches. The DIN connector for keyboard and mouse are actually mini-DIN connectors with 6 pins. The port was developed by IBM and is called PS/2.

CSIT 301 (Blum)21 RS 232 and DB-9 RS 232 is the old standard for local serial communication – data is sent bit-by-bit but grouped into bytes with a start bit and stop bit announcing the beginning and end of the byte. (There are newer standards, but the old name has stuck.) The standard serial connector is called the DB-9. Only two of the pins are used for data (receiving and transmitting, full-duplex) the rest are for control flow.

CSIT 301 (Blum)22 Pin Purposes 1.Carrier Detect - Determines if the modem is connected to a working phone line. 2.Receive Data - Computer receives information sent from the modem. 3.Transmit Data - Computer sends information to the modem. 4.Data Terminal Ready - Computer tells the modem that it is ready to talk. 5.Signal Ground - Pin is grounded. 6.Data Set Ready - Modem tells the computer that it is ready to talk. 7.Request To Send - Computer asks the modem if it can send information. 8.Clear To Send - Modem tells the computer that it can send information. 9.Ring Indicator - Once a call has been placed, computer acknowledges signal (sent from modem) that a ring is detected.

CSIT 301 (Blum)23 Parallel Communication A parallel connection sends many bits in parallel. The original advantage of this is that it is faster, but the disadvantage is that it is more complicated to do. Parallel connections are used most often for printers and removable storage drives, which need more speed than serial peripherals. Recently advances in serial connections have made them competitive with parallel connections. And devices such as printers conventionally thought of as strictly parallel devices are no longer thus.

CSIT 301 (Blum)24 Parallel Port The parallel port is used along with a local communication standard that transmits 8 bits (a byte) at a time. It is typically used for printers or scanners but sometimes used for external CD burner or zip drive. Female parallel port connector

CSIT 301 (Blum)25 Pin purposes Pins 2-9 carry the data. The other pins have purposes such as indicating if one is ready for data, indicating that data is being sent, acknowledging that data was received, etc. Pins can be used to have full-duplex communication (ability to send data in both directions simultaneously). The parallel-port standards are known as Enhanced Parallel Port (EPP) for non-printing devices and Extended Capabilities Port (ECP) for improved printing.

CSIT 301 (Blum)26 USB Universal Serial Bus (USB) is an attempt to have a universal port – a port which has reasonable speed, which many different devices can use at the same time, and which does not require expansion cards. The USB A connector which plugs into the computer

CSIT 301 (Blum)27 A USB socket in the back of the computer. Many computers have USB ports in the front. Some users are confused about the number of USB ports they have – assuming the front and back ports are distinct. (Some monitors have USB ports.) The USB B connector plugs into the device. Note that it is distinct from the USB A connector that plugs into the computer.

CSIT 301 (Blum)28 Connecting a USB device Connecting devices that use the serial port, parallel port or expansion slot require the system to be shut down, the device connected and then the system restarted. USB devices can be added while the system is up. This is known as hot plugging or hot swapping. –Distinct from Plug-N-Play (PNP)which is an older standard.

CSIT 301 (Blum)29 Up to 127 devices The USB standard supports up to 127 devices. A typical PC has one of two USB ports, one can connect more USB devices than there are USB ports by using USB hubs or daisy chaining.

CSIT 301 (Blum)30 The USB hub shown allows four devices to be connected to one USB port. One can plug a hub into a hub for even more connections. USB hubs may or may not need their own power depending on the needs of the devices plugged into them.

CSIT 301 (Blum)31 USB Cable A USB connection is simpler hardware than a standard serial connection using a DB9 connector. –It has two wires for power : +5 volts and ground. So devices that don’t require much power (e.g. a webcam) do not need an independent power source. – It has a twisted pair of wires for carrying the data. –Why is it twisted?

CSIT 301 (Blum)32 If your jump drive is not recognized, you may need to go to Control Panel/Administrative Tools/Computer Management/Disk Management, right click and change the letter for the jump drive

CSIT 301 (Blum)33 Enumeration The PC must detect all of the USB devices and assign them addresses. This is known as enumeration. The PC also determines the manner in which it will exchange data with the device. –Interrupt: small amounts of data at intermittent times –Bulk: larger chunks of data with error detection –Isochronous: real-time stream of data without error detection

CSIT 301 (Blum)34 Fire Wire The IEEE 1394 standard is for a fast serial cable that allows up to 63 devices to attach to a single port. Its high speed and isochronous data transfer make it useful for real-time data streaming. It supports Plug-and-play and hot plugging. Originally developed by Apple and known as firewire. Other companies have other names including Lynx and i.link.

CSIT 301 (Blum)35 Fire Wire Connector The standard supports a set of cables that have varying numbers of pins.

CSIT 301 (Blum)36 Networking Computers Two standard ways to make a computer part of a network are to use an internal modem or an Ethernet network interface card (NIC). Both use Unshielded Twisted Pair (UTP) wires. –Twisting reduces interference or cross-talk. –Shielding would reduce it more but is more expensive. The plugs used are the RJ-11 (modem) and the RJ-45 (Ethernet NIC)

CSIT 301 (Blum)37 RJ-45 Registered Jack-45, an eight-wire connector used to connect computers to an Ethernet LAN using UTP wire. RJ-45 connectors look similar to the RJ-11 connectors that are used for phones and modems, but RJ-45s are wider. –Additionally there are two sockets associated with an internal modem.

CSIT 301 (Blum)38 RJ-45 (LAN) and RJ-11 (phone)

CSIT 301 (Blum)39 Modem with socket for two RJ-11 plugs. UTP Ethernet connection with one RJ-45 plug.

CSIT 301 (Blum)40 References PC Hardware in a Nutshell, Thompson and Thompson A+ Certification: Exam Guide, Meyers and Jernigan