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Bus structures

Bus structures. Unit objectives: Describe the primary types of buses, and define interrupt, IRQ, I/O address, DMA, and base memory address Describe PCI and PCIe buses, and PCI and non-PCI video standards. Topic A. Topic A: Buses Topic B: The PCI bus. Buses. Communication pathway

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Bus structures

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  1. Bus structures Unit objectives: • Describe the primary types of buses, and define interrupt, IRQ, I/O address, DMA, and base memory address • Describe PCI and PCIe buses, and PCI and non-PCI video standards

  2. Topic A • Topic A: Buses • Topic B: The PCI bus

  3. Buses Communication pathway Defined by How many bits it transmits at one time Signaling technique Data transfer speed Three types Address Data Expansion (I/O) continued

  4. Buses, continued Address and data buses enable: Basic CPU operation Interactions with memory Expansion bus Communication pathway for non-core components to interact with the CPU, memory, and other core components Adapter cards add functionality PCIe is taking over from PCI Older buses: ISA, EISA, Micro Channel, and PC bus

  5. PCI bus slots

  6. The riser bus Brings the basic wiring and control of a function to a motherboard Decreases cost Two main riser standards: Audio/Modem Riser (AMR) Communications and Networking Riser (CNR)

  7. Activity A-1 Examining buses

  8. System interaction Gain the attention of the CPU Access shared memory locations Extend the system BIOS Transfer data across the bus

  9. Interrupts Signal CPU that attention is needed CPU stops what it was doing Services the device request Returns to its previous task

  10. IRQs Numerical identifiers Help CPU identify interrupt source Enforce priority of interrupts Common IRQs IRQ 1: Keyboard IRQ2: Cascade IRQs 8-15 IRQ4: COM1 IRQ6: Floppy IRQ12: PS/2 mouse IRQ14: Primary IDE hard drive

  11. Device Manager: IRQs

  12. Activity A-2 Examining IRQ assignments

  13. I/O addresses Identify devices Have a range of numerical addresses for each device Allow CPU to communicate multiple commands Use 16-bit hexadecimal numbers User or BIOS configures the number ranges

  14. Device Manager: I/O addresses

  15. Activity A-3 Viewing your computer’s I/O address assignments

  16. DMA channels DMA controller relieves CPU Dedicated channels Largely replaced by other techniques, such as bus mastering

  17. Activity A-4 Viewing your computer’sDMA channel assignments

  18. Memory addresses Devices extend system BIOS with new routines Display adapters SCSI controllers IDE controllers System BIOS locates and loads BIOS extensions using mapped memory location Historically in upper memory block (UMB) – space between 640KB (0x000A0000) and 1MB

  19. Device Manager: Base memory

  20. Activity A-5 Viewing your computer’s memory address assignments

  21. Topic B • Topic A: Buses • Topic B: The PCI bus

  22. PCI bus 32- or 64-bit bus Pentium PCs 33 or 66 MHz clock speed 133-533 MBps maximum data transfer rate Up to 8 functions on a single card Up to 5 cards/slots per system Requires PnP

  23. PCI adapter

  24. PCIe Newer standard Uses serial communication Lanes 2.5 Gbps in each direction using 8b/10b encoding (0.25 GBps) x1 (by one), x2, x4, x8, x12, x16, and x32 bus widths Links – bidirectional switched lanes Can up-plug (e.g., x1 card in x16 slot) Can’t down-plug (not officially)

  25. Multifunction cards PCI spec supports multifunction cards Up to 8 functions per card Five slots/cards per system Total of 40 expansion devices

  26. Activity B-1 Identifying a PCI bus

  27. Video adapters Generates signals sent to monitor Graphical interfaces involve massive amounts of graphics data Can be built into motherboard or adapter card Three types of video slots PCI PCIe AGP

  28. PCI-based video Low-end systems: video adapter built into motherboard PCI is slowest of three types Share bus with all other PCI-based devices Work well for two-monitor system

  29. PCIe-based video Designed to replace AGP cards x16 PCIe card has 4 GBps bandwidth Bidirectional nature allows up to 8 GBps Simultaneous data movement upstream and downstream Ideal for multimedia applications, such as gaming, photography, and videography See http://tinyurl.com/ylpk4lw for comparison among PCI standards

  30. A PCIe video card

  31. AGP video adapters Technically a port, not a bus Provides direct connection between video adapter and CPU Referred to as #X Original performance benefit was accessing and using main system memory Direct Memory Execute (DIME) Modern AGP cards use onboard memory, except in laptops Multiple-monitor support Being phased out for PCIe

  32. AGP adapter Note the hook

  33. AGP characteristics 32-bit bus Multiple of 33 MHz clock speed Speed “pumped” to as much as 533 MHz 266-2133 MBps data transfer rate PnP configurable

  34. AGP slots Typically brown; sometimes maroon or other dark color Separated from other bus slots to help cooling High-end systems include multiple, independent AGP slots

  35. Activity B-2 Identifying graphics connections

  36. Unit summary • Described the primary types of buses, and defined interrupt, IRQ, I/O address, DMA, and base memory address • Described PCI and PCIe buses, and PCI and non-PCI video standards

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