1. 9/28: Buses & Communication Buses: highways of the motherboard –system buses –local buses: PCI, ISA, EISA –expansion slots plug & play laptops: PCMCIA cards Ports: communicating with peripherals serial ports parallel ports SCSI ports USB & Firewire

2. Buses: highways of the motherboard Alternative to wiring everything individually Function like a highway Buses are made of traces, microchips, and expansion slots. Components share them Different types: –system buses –local buses: PCI, ISA, EISA image courtesy of TigerDirect

3. Traces Traces work like the wires in cables: the circuits are used for: –power –data transmission –control commands –& addresses, which are unique numbers assigned to each component on a bus. A component will ignore commands and data on the bus if another address is signaled. image courtesy of How Computers Work

4. Microchips in Buses Microchips are used in some buses to increase the capacity of the bus in speed, in the number of components, and to relieve the load on the CPU. image courtesy of How Computers Work

5. Expansion Slots Expansion slots are an easy way to expand and alter the computer’s setup. Plug & play: (PnP) a design that allows installation of adapter cards with reduced difficulty. image courtesy of How Computers Work

6. System Buses Connect the CPU to other components. Buses, like everything else in computers, have grown: current standard is 32-bit. Contain address lines, command lines and data lines –address lines tell what component is involved. –command lines carry commands for the component. –data lines carry the actual data for/from the component.

7. Local Buses The hubs of the local buses manage the connections and transfers of data, relieving load on CPU. ISA - Industry Standard Architecture: 8-bit and 16-bit, original one EISA - Extended ISA: 32 bit, better PCI - Peripheral Component Interconnect: 32 bit, operate at higher speeds (MHz), better yet. AGP – Advanced Graphics Port

8. Laptops: PCMCIA Cards PCMCIA cards function in a laptop like expansion cards function in a desktop No room in a laptop for physical expansion Networking, modems, etc. can be added to a laptop by using these cards. images courtesy of Toshiba, & Belkin

9. Ports: not quite buses For communicating with peripherals –printers, external modems, keyboards, scanners, etc. Major varieties: –serial –parallel –SCSI –USB –Firewire

10. Serial ports Four wires total: –One wire to transmit data, –One wire to accept data, –Two wires for electrical grounding. Common uses: –modems –mice

11. Parallel ports Nine or Twenty-Five wires total: –Eight wires to transmit data, –Other wires for electrical grounding, –Some wires for commands & communication. Common uses: –printers –scanners

12. SCSI ports Advantages: many –much faster than serial or parallel ports –provides ability to daisy-chain peripherals Disadvantages: few –expensive –uncommon Common uses: –printers –external drives (hard disk, tape, CD-ROM, etc.)

13. USB (Universal Serial Bus) ports Four wires total: –One wire to transmit data, –One wire to accept data, –Two wires for electrical power. Common uses: any peripheral –mice - scanners –external modems - joysticks –keyboards - printers images courtesy of www.allUSB.comwww.allUSB.com

14. aka IEEE 1394 Developed by Apple Will probably replace USB someday Daisy-chaining, faster Common uses: any peripheral –mice - scanners –external modems - joysticks –keyboards - printers images courtesy of Apple and firewirestuff.com Firewire ports