Computers: The clones and the add-ons

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The clones and the add-ons

Whatever the defects of IBM's personal computer, it had two uniquely redeeming features that have greatly helped the IT revolution:

• It was an open architecture machine, meaning that it was designed to be expandable by adding on additional circuitry.

• Its design can easily be copied.

The large growing PC market encouraged other manufactur­ers to exploit these features, to the advantage of everyone (except possibly IBM).

• There are many companies offering a variety of expan­sion cards, i.e. circuit boards containing chips which can be fixed in the expansion slots inside the PC's casing. These cards offer a range of facilities and enhancements, including improved screen displays, speech recognition, greater processing power, and so on.

• There are now many companies making and assembling personal computers which are virtually identical to the IBM PC and its successors. These are called PC-compat­ibles, or clones. They are able to run the same software as the real thing, but are normally cheaper and often offer superior performance.

What is so extraordinary is that although these computers comprise by far the largest segment of the market, IBM itself no longer manufactures them!

The IBM AT

As was explained earlier, the IBM PC was based on the Intel 8086 chip. This was looking distinctly long in the tooth by the mid 1980s, and it made the PC look weak besides some of the newer micros that were appearing, especially the Apple Macintosh (see below).

In August 1984 IBM launched the PC-AT ('AT' stood for 'advanced technology' - some would claim that this was more of a marketing ploy than a statement of truth!) This was designed to be compatible with the PC (i.e. run the same software) but to overcome some of the earlier machine's defects. One obvious external difference was the improved keyboard. Internally it had a more advanced CPU, based on the Intel 80286 chip. This enabled it to:

• Run a lot faster.

• Access memory above the 640K limit (in theory).

• Run several programs simultaneously (called multi­ tasking).

• Allow simultaneous use of the CPU and hard disk by several users (called multiusing).

In practice, however, the full potential of this machine has never been exploited, so that it has been used simply as a fast PC. The reason is that the enhancements to the operat­ing system necessary for it to access more memory and to multitask have yet to materialize (though in recent months Windows version 3 has appeared which does enable this).

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The Apple Macintosh

The original Apple microcomputer brought to birth personal computing in business. It was conquered by the IBM PC, but Apple fought back with the Macintosh, which appeared shortly before the IBM AT. The Mac was far ahead of its day in terms of both hardware and software. It was based upon a much more powerful processor, the 68000 chip, and it introduced a way of working with computers which is only now becoming standard on the IBM PC family.

This way of working was based upon Rank Xerox's original research work in the 1970s, and involved the use of the mouse to point to different parts of the screen and to pick options, the use of a graphical rather than character­ based display, and the use of icons (pictorial representations of computing entities such as files). Also, some excellent applications packages appeared for the Mac, which made full use of its graphical environment. A particular software innovation was desktop publishing, made possible by the Mac environment and the appearance, in the mid 1980s, of the desktop laser printer (see Chapter 3).

By 1987/88 the Mac was so far ahead in terms of graphics and publishing applications of anything that was available in the IBM PC world that it even seemed possible that it might topple IBM and its followers from their pre-eminent position. In the event, this has never happened. The reasons include:

• Corporate inertia against moving from the accepted standard.

• High prices ofthe Mac, and Apple's policy of keeping out competing manufacturers who would bring prices down.

• The knowledge that the PC world was moving towards, and catching up with, the Mac world.

Today, the IBM PC world has effectively caught up with the Mac in terms of the power of the hardware and the user interface. In retrospect, we can see that the value of the Mac was to popularize Xerox's revolutionary computer working environment, so that it is now the standard across almost the entire range of serious personal computing. As at the start of 1980s, at the start of the 1990s Apple has proved to be the pace setter but not the victor.

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The IBM PS/2

In 1987 IBM ceased production of PCs and ATs, and brought out in their place its new PS/2 range (short for Personal System/2). These are based on the same Intel chips as the PC and AT, and able to run standard PC software. However, they incorporated the superior Micro Channel Architecture (see below), and the superior VGA screen display (see page 67). They also offered a Mac-like comput­ing environment called 'Presentation Manager'. A further advantage for users with IBM mainframes is their ability to easily connect with these and so act as terminals.

IBM hoped that large numbers of corporate users would abandon the old PC/AT standard and flock to its new machine. In fact, this has yet to happen. PC/AT machines seem to go from strength to strength. They continue to outsell all others, they are steadily becoming more and more powerful, and they have adopted the VGA screen display standard. Besides this, the new Windows version 3 environ­ment for the PC is virtually identical to Presentation Man­ ager, and a huge amount of applications software is currently being written for it - far more than is being produced for Presentation Manager.

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