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System Buses

System Buses. Val Grinblat Dan Hummell Ryan McKenica. Introduction. 1980s More power Better performance Enhance operation. PC/XT. Released in 1981 Extension of the motherboard Processor and complete control 62 pins. AT Bus. Limited memory handling Therefore AT was developed

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System Buses

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  1. System Buses Val Grinblat Dan Hummell Ryan McKenica

  2. Introduction • 1980s • More power • Better performance • Enhance operation

  3. PC/XT • Released in 1981 • Extension of the motherboard • Processor and complete control • 62 pins

  4. AT Bus • Limited memory handling • Therefore AT was developed • Two separate oscillators

  5. Physical Differences • A second connector • Backwards compatible • Smooth bridge to the 16-bit data bus

  6. ISA Bus • Industry Standard Architecture • 16-bit addressing limit • Twice as many interrupts and DMA channels

  7. Problems with ISA • Complete access to system resources • No central registry • Limited number of interrupts • Limited number of available ports • Quatech

  8. Micro Channel Architecture (MCA) Bus

  9. History • IBM developed MCA bus in 1987 • Design began around 1983 • AT bus shows hint of MCA bus design • First 32-bit bus for the personal computer • Revolutionized design and standard of the bus • Replaced the PC/AT standard for PCs • Inspired by the best ideas from mainframe computers • IBM patents design to corner the market

  10. Features • Programmable Option Select • No longer need dip switches, jumpers, and headers • Small Architecture • Many grounds close to the high frequency digital signals • Smaller PCs • Multitasking • 32-bit bus width • First plug & play board

  11. Advantages • Microprocessor Speed vs. Bus Speed • 8 Mhz Bus Clock Signal lock • 10 Mhz Capability • Higher speed than ISA • Extra data lines:16 more data lines for 32 bits total • More address lines:4 gigabytes address memory • Channels for improved audio and video • Smaller mount components and expansion boards • FCC Certification easy to attain • Every fourth pin had electrical ground

  12. Disadvantages • Obsolete • Costly for manufactures and users to upgrade from PC/AT-based PCs • Not backward compatible with ISA-based boards • IBM had total control over architecture • Bus speed not fast enough for modern processors and PCs

  13. Extended Industry Standard Architecture (EISA) Bus

  14. History • Introduced in 1998 • “Gang of Nine” • Nine companies united to develop a design to match IBM’s MCA bus • Improvements based on MCA • Compatible with ISA-based systems • Not patent to one company • Molded from the AT bus design

  15. Features • Plug & Play feature • ISA cards work on EISA slots • Addressing Enhancement • 32-bit address bus • Bus width signaling • New transfer modes • Burst mode

  16. Advantages • Backward compatible with ISA • Supports bus mastering for greater efficiency • 32-bit bus width • Interrupt Sharing • Design was open to all manufactures

  17. Disadvantages • More expensive than other systems • Few EISA-based cards available • Performance is lower than more modern, popular buses such as the VESA local bus and PCI • Not widely used

  18. VESA or VL Bus Video Electronics Standards Association Bus Or Video Local Bus

  19. Brief History • Developed by the Video Electronics Standards Association • To replace slow ISA bus for video components and high-speed devices • Can be used a local video bus or an expansion bus

  20. Technical Details • Data width 32 bits • Bus speed 33MHz • Throughput 250 MB/sec • Transfer rate 8 times faster then the ISA bus • Bus connector original ISA slot plus additional VESA slot (see figure)

  21. Technical Details Cont • VESA bus connector • Two devices on one expansion card • Limited number of VESA devices connected to system board at one time

  22. What happen to the VESA bus? • It had a good design and good features • Plans from VESA for a 64-bit version of the bus for the Pentium processor • However, the PCI bus become more popular when the Pentium processor became the standard processor

  23. PCI Bus Peripheral Component Interconnect Bus

  24. Brief History • Developed in 1993 by the Intel Corporation • Originally design for better graphics capabilities on Intel computers • Has become the standard general-purpose bus • Used in PCs and Macintosh computers

  25. Technical Details • Data width 32 bits • Bus speed 33 MHz • Throughput 265 MB/sec • Can run at speeds different then the CPU • Short slot length then the both the ISA and VESA bus (see figure)

  26. Technical Details Cont • PCI bus connector • Plug and Play compatible • IRQ sharing • PCI Bridge

  27. Where is the PCI bus today? • Standard in most all PCs sold today • Still the standard general-purpose bus • Not often used for video adapters since development of the AGP bus

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