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Input/Output Organization III: Commercial Bus Standards

This document presents a comprehensive overview of various computer bus standards, including the IBM PC/XT and PC/AT buses, ISA, EISA, and MCA architectures. It discusses their specifications such as bus width, speed, and bandwidth, as well as their limitations. The document also explores the evolution of local buses like VESA and PCI, highlighting the need for high-speed connections for modern applications. It details Intel’s Northbridge/Southbridge architecture, AGP, PCI-Express, and SCSI, along with various types, underscoring the technological advancements in computer interfacing.

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Input/Output Organization III: Commercial Bus Standards

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  1. Input/Output Organization III: Commercial Bus Standards CE 140 A1/A2 20 August 2003

  2. Bus • Pathways of interconnections between different computer components • Three general types; data, address, control

  3. Bus characteristics • Bus width – how many bits can be transmitted at a time • Bus speed – how many bits can be transmitted across each wire per second • Bus bandwidth – bus width x bus speed (same as maximum throughput)

  4. IBM PC/XT Bus • Used on 8088-based systems • 8-bit bus • Copied by clone vendors for compatibility with third-party I/O boards

  5. IBM PC/XT Bus Source: Phil Storrs PC Hardware book <http://members.iweb.net.au/~pstorr/pcbook/showtell/show2.htm>

  6. IBM PC/AT Bus • Used on the 80286-based PC/AT • Maintained compatibility with the XT bus • Added an edge connector to increase bus width to 16-bits

  7. ISA • Industry Standard Architecture • Same as the PC/AT Bus • 16-bit, 8.33 MHz  Maximum throughput 16.7 MB/s • Limited bus master support

  8. ISA Source: <http://www.rackmountnet.com/ipc/isa_bk/isa_bk.htm>

  9. Problems with ISA • Slow • Limited number of interrupts • Lack of bus master support • Specific to Intel architecture  cards built using ISA will not work on non-Intel platforms • IBM-specific problem: no more monopoly on the hardware market

  10. MCA (IBM’s response) • MicroChannel Architecture • Developed by IBM for the PS/2 line • 16-bit/32-bit computer bus • 10-16 MHz • Intended to replace the ISA bus • Allows bus mastering • Limited plug and play • Limited to IBM hardware • Incompatible with XT, ISA boards

  11. EISA (Industry’s response) • Extended Industry Standard Architecture • Extends ISA bus to 32 bits • Maximum throughput: 33.3 MB/s • Increased bus mastering support • Maintains compatibility with old ISA boards

  12. EISA Source: <http://www.atmarkit.co.jp/fpc/slotsocket/indexpage/>

  13. Need for a faster bus • Original IBM PC: text-based applications • Advent of GUIs (Windows, et al) demand high performance

  14. Need for a faster bus • Example • 1024 x 768 display • 24-bit color • 30 frames per second •  67.5 MiB/s • ISA: 16.7 MB/s • EISA: 33.3 MB/s

  15. Local Bus Concept • Demand for higher bandwidth and increased throughput • Bus placed near (or on) the processor’s memory bus • “Local” to the processor • Does not have to go through the slower ISA bus

  16. VESA Local Bus • Developed by Video Electronics Standards Association (VESA) • High-speed conduit for memory-mapped I/O and DMA • Intended for high-bandwidth peripherals (video, storage, etc.) • 33 MHz, 32-bit • Extension of the 486 memory bus

  17. VESA Local Bus Source: <http://www.lco-college.edu/classes/pc-ware/chap4b.html>

  18. PCI • Peripheral Component Interconnect (PCI) • Developed by Intel (90’s) but standard was made public  platform independent • 33 Mhz, 32-bit  Maximum throughput 132 MB/s • Plug-and-Play

  19. PCI Source: <http://www.ontrack.com/hardwareinfo/input-output.asp>

  20. PCI Variants • PCI 2.2: 64-bit, 66 Mhz  Maximum throughput: 533 MB/s • PCI-X: 64-bit, 133 Mhz  1066 MB/s • PCI-X 266 (PCI-X DDR)  2133 MB/s • PCI-X 533  4 GB/s • Mini PCI – small form factor PCI cards for use with embedded systems/portable systems

  21. Problem with using PCI alone • Still not fast enough for memory • Not compatible with ISA cards

  22. Intel’s Solution: Northbridge/Southbridge Architecture • Uses bridge chips • PCI Bridge (Northbridge) • Connects CPU, memory, and PCI bus • ISA Bridge (Southbridge) • Connects PCI bus to the ISA BUS and also supports one or two ATA disks • Advantage: • High-bandwidth memory bus (Front Side Bus) • PCI bus available for high-bandwidth peripherals • Next generation: Intel Hub Architecture

  23. Northbridge/Southbridge Architecture Source: Structured Computer Organization by Tanenbaum

  24. AGP • Accelerated Graphics Port • High-speed computer bus designed for 3D computer graphics acceleration • AGP 1X: 32-bit, 66 MHz • Also available: 2X, 4X, 8X

  25. AGP Source: http://www.watch.impress.co.jp/pc/docs/article/991008/hotrev30.htm

  26. PCI-Express • Next generation PCI implementation from Intel • Intended to replace AGP and PCI altogether • Not fast enough as a memory bus • Alternatives: HyperTransport

  27. SCSI • Small Computer Systems Interface • Pronounced “scuzzy” • Higher transfer rate than ATA disks • Used in workstations and servers • More than just a hard disk interface, a full-fledged bus • Also supports CD-ROMs, CD-recorders, scanners, tape units, etc. • Devices are daisy-chained in a linear manner • Terminated at the end to prevent reflection

  28. SCSI Types

  29. SCSI • Typical 8-bit SCSI cable • 50 wires, 25 ground, 8 for data, 1 for parity, 9 for control

  30. IEEE 1394 • Developed primarily by Apple • Commonly referred to as Firewire (Apple), i.Link (Sony) or digital video (DV) port • Used for data storage devices and digital video cameras • Does not require a host • IEEE 1394a: up to 400 Mbps • IEEE 1394b: up to 800 Mbps • Allows daisy-chaining, plug-and-play, and hot-swapping

  31. USB • Universal Serial Bus • Developed as a replacement to the serial and parallel ports • USB 1.1 – Up to 12 Mbps • USB 2.0 – Up to 480 Mbps • Up to 127 devices (THEORETICAL!) • Daisy-chained in a tree structure • Requires a host computer • Upcoming: USB On the Go

  32. Storage Interfaces • ATA • Serial ATA • SCSI • IEEE 1394 • USB

  33. ATA • Advanced Technology Attachment • Standard interface for connecting storage devices • Transitioned from PIO to DMA modes • With the advent of Serial ATA, it has been retroactively renamed Parallel ATA

  34. ATA Types • Most new drives support Ultra DMA Modes (in contrast to Programmed I/O modes) • Ultra ATA/33 – 33 MBps • Ultra ATA/66 – 66 MBps • Ultra ATA/100 – 100 MBps • Ultra ATA/133 – 133 MBps

  35. ATA-VI • Supports 48-bit addressing that allows system to address 144 PB • Breaks the 137 GB size barrier imposed by older ATA standard

  36. ATA Cables

  37. Serial ATA • Higher speed than Parallel ATA • Hot-swappable • Cable: 7-wire cable versus 40/80-wire cable • Power cable: 15 pins • Initial speed: 150 MBps • Later implementations: 300 MBps, 600 MBps

  38. Serial ATA Cables

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