Microprocessor Future Trends

There's no question that microprocessors will continue to grow more complex over time. We're nowhere near reaching any natural limit to microprocessor growth. Where once it seemed silly to design a computer-on-a-chip—after all, how many computers does the world need—now it seems just as absurd to stop.

The actual size of microprocessor chips is growing only slowly, but the complexity within them is growing much faster because semiconductor technology permits engineers to squeeze more transistors into less space. Microprocessors with 1 million transistors were surpassed by 10-million-transistor processors after only a few years. Microprocessors with 100 million transistors weren't far behind. This trend continues with no end in sight.

The bigger question is this: How will engineers fill the space? How will they spend their 500-million-transistor budgets? The answer has historically come from above, from mainframe systems and supercomputers. For decades, microprocessors shadowed the developments of high-end computers, first lagging by several generations but now lagging the high-end machines by only a few years. Microprocessors have been nipping at the heels of the computer makers for years, which is why so many big computer companies went out of business in the 1990s. Rather than fight the trend, some computer makers joined the bandwagon and designed their machines around commercial microprocessors, but then had a hard time differentiating their products from other companies with the same strategy and access to the same chips.

Future trends point toward cooperation. Even though microprocessors get about 30 percent faster every year, they're not doing that much more useful work. Instead of performing single tasks even faster, future chips are likely to perform more simultaneous tasks, but slower. A team of 12 bricklayers is more productive than one really fast bricklayer working alone. By the same token, teams of microprocessors working on a problem together will likely generate a better return on the investment of transistors.

Cooperation within a single chip is one way to go. Called instruction-level parallelism (ILP), microprocessors today can execute a few instructions in parallel. This approach can't grow forever, though. Superscalar processors can become so complex that they don't deliver enough extra performance to be worth the extra silicon. ILP has already moved microprocessors about as far forward as it can. It has worked for the past few years, but it's an approach that's running out of steam.

Taking the problem outside the chip is another approach. Chip-level symmetric multiprocessing (SMP) promises to keep many microprocessors working in concert. Large supercomputers do this already, on the theory that two (or more) heads are better than one. Using several chips together has economic advantages, too. Individual microprocessors won't have to be so large (read: expensive) and it might be possible to add or remove processors from a system when upgrading. The problems lie mainly in the software. It's not trivial to program a computer with multiple processors, any more than it is to command multiple cooks working in the same kitchen. Orchestrating that much computing horsepower is a talent few programmers have thus far demonstrated.

RISC concepts seem to be slowly losing currency as chip complexity increases. Paradoxically, the RISC design philosophy arose just as transistor budgets were expanding. Why economize on silicon when transistors are almost free? Why put the burden on software when programmers are scarce and highly paid? Chip designers have learned they can make their microprocessors more complex and still have them run faster. We get to have our cake and eat it, too. Whichever architectural approach gains prominence, tomorrow's microprocessors are guaranteed to be more complex than today's.

The other guarantee is that microprocessors will become even more ubiquitous. In the early 1900s electric motors were rare and precious commodities (so was home electricity). Catalogs and dry-good stores sold myriad attachments and add-ons for householders who presumably had only one electrical motor in the home, if that. Today, electric motors are so prevalent in blenders, tape players, cooling fans, and executive toys that we don't notice them. If they wear out or break we throw them away because it's not worth the effort to repair them.

Tomorrow's microprocessors will go from being in everything to being in everything many times over. The average cellular telephone won't have one or two microprocessors in it; it will have 15. Cars will become rolling computer farms. Children's toys will be the envy of the NASA space program. Gumball machines will dispense 64-bit souvenirs, after you wave your computerized debit card in its general direction. Microprocessors will be like pennies on the sidewalk: shiny and interesting but not worth picking up off the ground.