* Mainframe access. If you need your microcomputer to communicate with a mainframe, a communications processor can improve the link by translating microcomputer requests for information into a form readily understood by the mainframe and vice versa. Communications processors will replace the simple links now available, in which the micro serves as a "dumb" terminal to the mainframe.
1991-1992
* Voice messages. A new class of software and hardware will record and play back voice messages directly on your computer. Such recordings will become a form of voice mail, traveling over computer networks as electronic mail does today. A voice message could be self-contained ("We'll meet with the new CEO for lunch on Monday"), or it could travel with and annotate a computer file, such as a spreadsheet ("This analysis assumes sales will meet the projections Peter described at yesterday's meeting"). Some products offering voice annotation -- Wang Laboratories Inc.'s Freestyle, for instance -- are already available; they will blossom along with fast networks and sound processors.
1993-1996
* Simulation. Computer simulations of real-world affairs -- such as econometric models of the garment industry or a mock-up of an assembly line -- require prodigious computing power. Today such simulations can be done only on a mainframe computer, but auxiliary processors will make them possible on a micro. A fast processor designed to manipulate mathematical arrays, for example, could compute mathematical models much faster than even the math coprocessors that are common today.
* File and database processing. Software of the mid-1990s will construct automatic links among files. When you type someone's name to start a letter, for instance, your software -- behind the scenes -- will automatically look up all previous correspondence with that person as well as your correspondent's mailing address and any information related to the topic of your letter. Maintaining automatic links like these takes more computing power than the CPU can effectively supply. Instead, a specialized database processor will independently search through and match text, automatically updating its own dictionary and lists of synonyms.
Eventually such features will be so compelling that all microcomputers will support them, and the definition of a high-performance bus will shift upward once again.
THE BUS STOPS HERE
A guide to the various buses on the market
Buses have evolved to keep pace with the increasing speed and sophistication of central processing units and computer software -- starting with the first 8-bit designs (so called because the bus could transfer 8 bits of information at a time) to 16- and 32-bit designs.
* The XT bus. This is the original 8-bit bus introduced in the IBM PC in 1981 to support computers based on the Intel 8086 and 8088 CPUs. The bus quickly became a standard, and hundreds of companies produced hardware circuit boards that could be plugged into it. Most low-end PCs and compatibles, including the IBM PS/2 Model 25 and some Model 30s, still use this bus.
* The AT bus. This is a 16-bit modification of the XT bus that was created simply by adding an extra connector to the original XT bus. IBM first introduced it in the PC/AT in 1984. Nearly all desktop machines based on Intel's 80286 chip and produced today incorporate the AT bus. IBM still uses the AT bus in the PS/2 Model 30/286. The AT bus is also used with a hybrid CPU, the 80386SX, which is found in machines such as the Compaq Deskpro 386s. Most circuit boards for the PC/XT will work on an AT bus, except for memory boards, disk-drive controllers, and other boards that require fast information exchange with the CPU.
* Modified AT buses. Virtually every 80386 microcomputer available today, except for IBM's, uses a proprietary 32-bit modification of the AT bus. These modifications are all mutually incompatible, although many accessory boards for XTs and ATs work in these computers. Because there are so many of these buses, no advanced accessories will be developed for any of them.
* MCA (microchannel architecture) bus. For all of its 80386 models and some of its 80286 models, IBM broke away from the XT and AT buses and developed a completely new design. MCA is better engineered than the earlier buses, and accessory MCA circuit boards are "self-configuring," which makes them easier to install; you can plug them in without having to set a complicated series of switches. IBM is the dominant supplier of MCA computers, although a few other companies, such as Tandy Corp., also make them.
* EISA (extended industry standard architecture) bus. This is in effect a standardized 32-bit modification of the AT bus, which should eventually supersede other modified 32-bit AT buses. Like MCA circuit boards, new EISA boards are supposed to be self-configuring. The EISA bus should also accept many old XT or AT boards, although these would not be self-configuring. At present, the EISA specification is unfinished, and no hardware exists. EISA backers expect the first computers by the end of 1989.
