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Chapter 38. Replacing Your Main System Board > How System Boards Have Changed

How System Boards Have Changed

Main system boards have undergone dramatic changes since IBM released its first PC back in 1981. Most of the major changes and advances seen in system board design have resulted from changes or advancements in bus design, chipsets, and processors. Here is a brief overview of the six major bus designs that have been incorporated into PCs since 1981:

  • 8-bit (or “original IBM PC”) bus. The original 8-bit bus design used in IBM PCs, XTs, and early PC-compatible computers.

  • 16-bit ISA bus. The first 16-bit bus was essentially a 16-bit upgrade of the original IBM PC bus; the ISA (Industry Standard Architecture) bus was used originally in the IBM AT computer and AT-compatible computers.

  • Micro Channel Architecture bus. IBM's proprietary 32-bit bus; used in its PS/2 computer line. No manufacturer other than IBM ever used this bus design because other manufacturers did not want to pay license fees to IBM.

  • EISA bus. The computer industry's response to IBM's proprietary MCA bus; used mainly in network file servers manufactured by Compaq; EISA stands for Extended Industry Standard Architecture. In addition to the EISA bus cards, you can also use ISA bus cards.

  • VESA local bus. The first 32-bit bus design used in 486 computers that was fast enough to support graphical environments.

  • PCI bus. Designed to overcome many of the speed limitations of the VESA local bus to support the higher bus speeds required by the Pentium processor line.



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