Computers: The Past, Present, and Future -- Present

Computers: Present: Tutorial

MCA

Shown here is a MCA expansion slot.

MCA, developed by IBM, was the first bus capable of changes through software. It offers the user a slight increase in speed over the original ISA connector, and it provides the user with the option to use 16 or 32 bits. The MCA bus’s advantages where not enough to outweigh its disadvantages. Since IBM copyrighted the MCA slot technology, developers had to pay a large amount of their profits to IBM. In addition, it was incompatible with the original ISA bus. These problems contributed greatly to its shortfall. In appearance, the MCA bus looks extremely similar to the ISA bus. MCA cards are also identifiable by their tendency to have a blue handle on one or both ends.

Shown here is a MCA expansion card.

EISA
"The Best of Both Worlds". The EISA (Extended ISA) was developed by the "gang of nine", a group of large computer companies interested in developing an open technology that was better than the ISA bus. The EISA bus combined many of the original features of the MCA expansion slot, while leaving it compatible with the original ISA configuration. EISA buses were generally used in servers; however, the PCI bus is now quickly replacing them. You can identify an EISA bus by its similarity to an ISA bus.
VL-Bus
The VL-Bus, also known as the VESA or VLB, was developed to operate on speeds faster than any previous bus could handle. One of the first components introduced to this slot was video circuitry. The VESA bus was simply an extension of an ISA bus. The connector was lengthened to add another 32-bit connector onto the end of the original long ISA connector. High throughput devices commonly use the VESA slot.
Continue the tutorial with the next section on PCI slots.

All material and images on these pages are copyright Joseph,Ed. This page was developed for the Thinkquest1999 competition.