Information Technology Reference
In-Depth Information
duced the Model 25, also with an 8 MHz Intel 8086, which had no hard drive, and a re-
duced keyboard for $1350.
•
Model 50 and 60, which used a 10 MHz 80286 with MCA.
•
Model 80, which used a 20 MHz 80386 with MCA.
In 1988, the battle lines had been drawn the year before. IBM was trying to pull the market
towards their architecture. The strength, of this was highlighted by John Akers, the then IBM
Chairman:
We're trying to change the habits of an awful lot of people. That won't happen overnight, but
it will bloody well happen.
IBM thought they would win the battle, and the older IBM PC architecture would die off.
Several companies went with IBM, including Tandy (Tandy 5000MC), Dell and Olivetti. But
the first signs of problems for IBM came when 61 companies developed the 32-bit version of
the ISA bus, the EISA (Extended Industry Standard Architecture). This allowed 32 bits to be
transferred at a time. Unfortunately, it was still based on an 8 MHz clocking rate, which gave
it a data throughput of 32 MB/s. It was supported by the leading computer companies, such
as Compaq Computer, AST, Epson, Hewlett-Packard, NEC Technologies, Olivetti, Tandy,
Wyse, Zenith, and Microsoft. Along with this, Compaq Computer and eight other companies
started developing the ISA standard to improve the AT-bus. Rod Canion, the Compaq Com-
puter and CEO, showed his company's resistance to the MCA bus:
If people are going to buy Micro Channel, they're going to buy it from IBM.
The market would eventually reject the MCA bus, mainly because of the weight of the new
x86, 80386 computers on the market. It would take a company such as Intel to develop a
totally new bus system: the PCI bus.
3.9
Notes from the author
Oh boy, is it confusing! There are so many different busses used in systems, especially in
PCs. There are three main reasons for the number of busses: legacy, compatibility and effi-
ciency. With legacy, busses exist because they have existed in the past, and are required to
be supported for the time being. With compatibility, busses allow the segmentation of a sys-
tem and provide, most of the time, a standard interface that allows an orderly flow of data
and allows manufactures to interconnect their equipment. If allowed, many manufacturers
would force users to use their own versions of busses, but the trend these days is to use inter-
nationally defined busses. Efficient busses have been designed to take into account the type
of data that is being transmitted. So, in the end, we win.
Sometimes, though, the bus technology does always win, and manufacturers who try to
develop systems on their own can often fail miserably. This has been shown with the MCA
bus, which was an excellent step in bus technology, and made up for the mistakes made in
the original PC design. But, IBM tried to force the market, and failed. In these days, it is
international standards that are important. Products to be accepted in the market or in the
industry require an international standards body to standardise them, such as the IEEE, the
ISO, ANSI and so on. Without them, very few companies will accept the product. A classic
