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VL-bus

(VESA Local-BUS) A peripheral bus from VESA that was primarily used in computers with 486 CPUs. VL-bus provided a high-speed data path between the CPU and peripherals (video, disk, etc.). It was a 32-bit bus that supported bus mastering and ran at speeds up to 40 MHz. With up to three VL-bus slots on the motherboard, each slot was in two parts: one Micro Channel slot along with an ISA, EISA or a second Micro Channel slot. See PC data buses.




The VL-bus
The VL-bus was widely used on 486 motherboards, providing a wider bandwidth for peripheral data transfer than the traditional ISA bus.





Types of Expansion Cards
Of all the bus types in this illustration, PCI is the only one found in new computers. AGP, ISA, EISA, Micro Channel and VL-bus are obsolete.






PC data buses

The bus in a PC is the common hardware interface between the CPU and peripheral devices. Parallel buses use multiple lines (wires) for data. Serial buses use one line for data. Following are the various buses used in the PC.

Current

PCI Express - (Parallel in Serial Form)
PCI Express (PCIe) is the current bus interface, superseding PCI. New PC motherboards generally have only PCIe slots. See PCI Express.

PCI - (Parallel)
PCI was very popular in PCs, Macs and other hardware platforms. Superseded by PCI Express (PCIe), motherboards may be available with one PCI slot. See PCI.

USB - (Serial)
USB is used extensively to permanently or temporarily attach myriad devices, including drives, printers, cameras and flash drives. See USB.


Previous

FireWire - (Serial)
FireWire was mostly used for digital camera connections. Popularized by Apple, adapters were required to use FireWire on new Macs. See FireWire.

AGP - (Parallel)
The AGP was designed for faster screen display, and one slot was found on motherboards. AGP was superseded by PCI Express. See AGP and display adapter.

ISA - (Parallel)
Pronounced "eye-suh," ISA evolved from the first PC bus in 1981 and originated on IBM's PC AT in 1984. See ISA.

Micro Channel - (Parallel)
IBM introduced Micro Channel with its PS/2 line in 1987, then later supported ISA and eventually gave up Micro Channel for PCI. See Micro Channel.

EISA - (Parallel)
Pronounced "ee-suh," this extension of ISA was created to counter Micro Channel. EISA slots also accepted ISA cards. EISA was used in servers but later abandoned for PCI. See EISA.

VL-bus - (Parallel)
The VL-bus was introduced during the 486 era and offered more speed than ISA. It too gave way to PCI. See VL-bus.




Types of Expansion Cards
Except for PCI Express and PCI, all the rest of these interfaces have been discontinued.






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