Chapter 2
The PowerPC Technology

“At our core, we are a technology company,” said Lou Gerstner shortly after he took over as IBM’s chief executive in 1993. IBM has always been a technology company. Just about every technology that drives the computer industry, from RISC to relational databases, came from IBM. In the past, IBM has failed to capitalize on many of the technologies it invented, and Gerstner intends to change that. He has stated that his highest priority is to exploit IBM’s technologies by driving certain key technologies throughout its product lines. The PowerPC RISC microprocessor in the AS/400e series is one of those key technologies for IBM.

Those Incredible Shrinking Chips

Industry figures show that today there are between 300 billion and 400 billion chips in the world, mostly memory chips. The rapid advances in silicon microchip technology over the past few years have made it possible to deliver this many chips. Included in these numbers are about 15 billion microprocessor chips. The vast majority of these microprocessor chips are used not in computers but in watches, TV sets, kitchen appliances, and automobiles. A new automobile, for example, typically has 10 to 12 microprocessors, and some models have considerably more.

With each new generation of chips, manufacturers have been able to pack more transistors on to a single chip, roughly doubling the number of transistors every 18 months. This is known as Moore’s Law, after Gordon Moore, Intel Chairman and co-founder who predicted the doubling phenomenon more than 25 years ago. In 1971, Intel introduced its first microprocessor, the 4004, with 2,300 transistors on a single chip. Today, a single processor chip has millions of transistors. Moore’s Law has held for more than a quarter of a century.

Technology’s capability to continuously shrink the size of the transistors on a silicon chip accounts for this increasing density. Many industry sources now predict that soon after the year 2000 the width of a transistor on a chip will be only about 0.18 microns; and in less than a decade, chips with 0.08-micron transistors will become available. To put this into perspective, a human hair is approximately 80 microns wide. Imagine being able to put a thousand transistors across the width of a human hair.

This transistor shrinkage will ensure that Moore’s Law holds for several more years. In less than 10 years, we likely will see chips with more than 100 million transistors; and 1 billion transistors on a chip may be possible in less than 15 years. All of this will be accomplished using the same silicon technology we use for today’s microchips. The need for an alternative technology is probably at least 20 years away.

A problem exists, however, with these high-density chips. They are enormously complex and are becoming extremely expensive to develop and manufacture. The economics of semiconductor manufacturing will likely squeeze several current chip manufacturers out of the business. For example, a silicon foundry capable of producing today’s microchips costs a little more than $2 billion. A silicon foundry capable of manufacturing chips with transistors smaller than 0.1 micron will likely cost $10 billion. With the continuing drop in semiconductor chip prices, many of us believe there will be only about 10 chipmakers left a decade from now.

No one knows who these chipmakers will be, but even the most successful vendors today have no guarantees for tomorrow. Look at Intel, for example. Many people would guess that because of the popularity of PCs, Intel is the largest vendor of microprocessors. But that’s not true; Intel produces only about 1.5 percent of all microprocessors. Motorola, Hitachi, and even Zilog (does anyone remember the Z80?) all sell far more microprocessors than Intel does. Intel’s success is due primarily to the high prices it commands for its PC chips. Other vendors sell chips with equal performance at a fraction of the price. But as long as there are PCs, Intel can charge premium prices.

IBM is determined to be among those surviving chip manufacturers in the next decade, and PowerPC is a big part of that effort. As we will see shortly, the PowerPC technology will be a fundamental part of the AS/400 and other IBM products for the next several years. In the rest of this chapter, we examine in more detail the evolution of the PowerPC architecture and how the AS/400 uses this architecture. We then take a closer look at the processors used in the various AS/400 RISC models.