I/O bus support
The chipset determines what I/O bus standards the motherboard can support. The chipset manages the I/O busses, arbitrating data transfer between them, the CPU, and system memory. The chipset features determine which I/O busses the system supports, the speed at which the busses operate, and what additional related system features are supported. Depending on how you count, half a dozen or more I/O bus standards have been in common use since the first PCs. In order of their appearance, they include:
- Industry Standard Architecture (ISA)
Used in 8-bit form in the PC and XT and 16-bit form in the PC/AT. Obsolete, but most motherboards made through 2000 provided at least one ISA slot for legacy cards. By late 2000, many new motherboard models shipped without ISA slots. Good riddance, we say.
- MicroChannel Architecture (MCA)
An IBM standard that never caught on. Obsolete.
- Extended Industry Standard Architecture (EISA)
An open standard developed by Compaq and eight other PC makers (the so-called “Gang of Nine”) to compete with the proprietary MCA, but which achieved only limited acceptance, primarily in servers. Obsolete.
- VESA Local Bus (VLB)
An open standard that was widely used in 486 systems, but whose technical shortcomings made it inappropriate for Pentium and later systems. Obsolete.
- Peripheral Component Interconnect (PCI)
An open standard developed by Intel, used on late-model 486 systems and almost universally for Pentium and later systems. Older PCI systems use ...
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