LOCAL BUSES(Exercise 2)

A computer bus is a method of transmitting data from one part of the computer to another part of the computer. The computer bus will connect all devices to the computer CPU and main memory. The computer bus consists of two parts, the address bus and a data bus. The data bus transfers actual data, whereas the address bus transfers information about where the data should go.
This page contains a basic overview of each of the computer buses as well as related links to each bus.
ISA
Introduced by IBM, ISA or Industry Standard Architecture was originally an 8-bit bus that was later expanded to a 16-bit bus in 1984. When this bus was originally released it was a proprietary bus, which allowed only IBM to create peripherals and the actual interface. However, in the early 1980's other manufacturers were creating the bus.
In 1993, Intel and Microsoft introduced a PnP ISA bus that allowed the computer to automatically detect and setup computer ISA peripherals, such as a modem or sound card. Using the PnP technology, an end-user would have the capability of connecting a device and not having to configure the device using jumpers or dipswitches.
To determine if an ISA card is an 8-bit or 16-bit card, physically look at the card. You will notice that the first portion of the slot closest to the back of the card is used if the card is an 8-bit card. However, if both sections of the card are being utilized, the card is a 16-bit card.
Many manufacturers are trying to eliminate the usage of the ISA slots; however, for backwards compatibility you may find 1 or 2 ISA slots with additional PCI slots, AGP slots, etc. However, today you may also have a motherboard that has no ISA slots. We highly recommend, when purchasing any new internal expansion card, that you stay away from ISA as it has, for the most part, disappeared.
MCA
Short for Micro Channel Architecture, MCA was introduced by IBM in 1987. MCA, or the Micro Channel bus, was a competition for ISA bus. The MCA bus offered several additional features over the ISA such as a 32-bit bus, automatically configure cards (similar to what Plug and Play is today), and bus mastering for greater efficiency.
One of the major downfalls of the MCA bus was it being a proprietary bus and because of competing bus designs. The MCA bus never became widely used and has since been fazed out of the desktop computers.
EISA
Short for Extended Industry Standard Architecture, EISA was announced September of 1988. EISA is a computer bus designed by 9 competitors to compete with IBM's MCA bus. These competitors were AST Research, Compaq, Epson, Hewlett Packard, NEC, Olivetti, Tandy, WYSE, and Zenith Data Systems.
The EISA bus provided 32-bit slots at an 8.33 MHz cycle rate for the use with 386DX or higher processors. In addition, the EISA can accommodate a 16-bit ISA card in the first row.
Unfortunately, while the EISA bus is backwards compatible and is not a proprietary bus, the EISA bus never became widely used and is no longer found in computers today.VLB
The VESA (Video Electronics Standards Association) is a nonprofit organization founded by NEC. The VLB, or VESA Local Bus, 1.0 was released in 1992. The VLB is a 32-bit bus that had direct access to the system memory at the speed of the processor, commonly the 486 CPU (33 / 40 MHz). VLB 2.0 was later released in 1994 and had a 64-bit bus and a bus speed of 50 MHz. Unfortunately, because the VLB heavily relied on the 486 processor, when the Pentium Processor arose in the Market place, manufacturers began switching to PCI.
PCI
Introduced by Intel in 1992, revised in 1993 to version 2.0, and later revised in 1995 to PCI 2.1. PCI is short for Peripheral Component Interconnect and is a 32-bit computer bus that is also available as a 64-bit bus today.
The PCI bus is the most commonly used and found bus in computers today.