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Internal Buses in Hardware

August 6, 2009
tags:
Connections to various internal components.
The Peripheral Component Interconnect or PCI Standard specifies a computer bus for attaching peripheral devices to a computer motherboard.

Year Created
July 1993
Created by
Intel
Superseded by
PCI Express (2004)
Width
32 bits
No of Devices
1 per slot
Capacity
133 MB/s
Style
Parallel
Hot Plugging
No
External
No

PCI Slot

PCI Express, abbreviated as PCI-E or PCIe, is a computer expansion card interface format introduced by Intel in 2004.
PCI Express was designed to replace the general-purpose PCI (Peripheral Component Interconnect) expansion bus.
Year Created
2004
Created by
Intel
Width
1 bit
No of Devices
1 per slot
Capacity
8 GB/s (v1.1,x32)
Style
Serial
Hot Plugging
Depends on form factor
External
Depends on form factor

Universal Serial Bus (USB) is a serial bus standard to interface devices.
It allows the peripherals to be connected in a single standardized interface socket and to improve plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the computer (hot swapping).
USB can connect computer peripherals such as mouse devices, keyboards, PDAs, game pads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives.

USB

Hyper Transport (HT), is formerly known as Lightning Data Transport (LDT).
It is a bidirectional serial/parallel high-bandwidth, low-latency point-to-point
link that was introduced on April 2, 2001
Common System Interface or “CSI” is a point-to-point processor interconnect being developed by Intel, as a competitor     to Hyper Transport.
    • AGP (being phased out)
The Accelerated Graphics Port also called as Advanced Graphics Port is shortened to AGP.
AGP is a high-speed point-to-point channel for attaching a graphics card to a computer‘s motherboard, primarily to assist in the acceleration of 3D computer graphics.
AGP was replaced by PCI Express but still AGP cards and motherboards are still available to buy, but has become much less common.

Year Created
1997
Created by
Intel
Superseded by
PCI Express (2004)
Width
32 bits
No of Devices
1 per slot
Capacity
2133MB/s
Style
Parallel
Hot Plugging
No
External
No

An AGP slot (maroon, although the color is usually brown) and two PCI slots

    • VLB (outdated)
The VESA Local Bus is abbreviated to VL-Bus or VLB.
A VLB slot itself was an extension of an existing ISA slot. The extended portion was usually coloured a distinctive brown.
VLB acted as a high-speed conduit for memory-mapped I/O and DMA, in personal computers.
But both VLB and ISA cards could be plugged into a VLB slot (not at the same time).
The length of a VLB slot led to another new acronym “Very Long Bus”.

VLB and ISA slots on a motherboard

    • ISA (outdated)
Industry Standard Architecture originated as an 8-bit system in the IBM PC in 1981.
ISA was extended in 1983 as the XT bus architecture.
ISA is designed to connect peripheral cards to the motherboard, which allows bus mastering only for the first 16 MiB of main memory that is available for direct access.
Bus mastering
Bus mastering is a feature supported by many bus architectures that enables a device connected to the bus to initiate transactions.

Year Created
1981
Created by
IBM
Superseded by
PCI (1993)
Width
8 to 16 bits
No of Devices
1 per slot
Capacity
8 MHz
Style
Parallel
Hot Plugging
No
External
No

Five 16-bit and one 8-bit ISA slots on a motherboard
The Extended Industry Standard Architecture (EISA) is a bus standard for IBM compatible computers.
The bus mastering support is also enhanced to provide access to 4 GB of memory. Most EISA cards produced were either SCSI or network cards.

Year Created
1988
Created by
Gang of Nine
Superseded by
PCI (1993)
Width
32 bits
No of Devices
1 per slot
Capacity
8.33 MHz
Style
Parallel
Hot Plugging
No
External
No

Three EISA Slots.
    • MCA (outdated)
Micro Channel Architecture (MCA) was a 16- or 32-bit parallel computer bus created by IBM in the 1980s for use on their new PS/2 computers.

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