In 1984, the Macintosh 128K burst onto the computing scene. Well, okay, it crept onto the scene. The "computer for the rest of us" was a risky venture that could easily have fizzled. The world was ready for the Mac's graphical user interface; Apple just needed to explain that fact to the planet's unsuspecting inhabitants in an evangelical PR campaign. In the decade that followed, all Macs that ever lived were built around a single family of microprocessors, the Motorola 68000 and its descendants.

But no more; the PowerPC chip has been born, and the 680x0 clan appears headed for the spare-parts bin. The product of a once-unthinkable alliance between Motorola, Apple, and IBM, the PowerPC family of high-speed microprocessor chips will be the brain of most Apple and IBM personal computers in the future.

Apple, for one, is putting all its high-tech eggs in the PowerPC basket. In the midst of another evangelical PR campaign, the company is moving quickly to phase out most of its high- and mid-level 680x0-based Macs and almost certainly will phase out the rest of them in the next year or two. The Quadra AVs, 610, 650, and 800, will almost certainly be history in the near future.

Of particular interest to musicians, the blazing speed of the PowerPC makes the new computers capable of recording and playing 16-bit digital audio without using a DSP coprocessor. As we'll see later, however, there appear to be several "ifs" and "buts" to this capability.

Taking RISCs
The PowerPC chip is not simply a faster conventional microprocessor; it has a completely different architecture than the chips used in previous desktop computers. The Intel 80x86 and Motorola 680x0 chips that provide the brain power for Ataris, Amigas, PC-compatibles, and pre-PowerPC Macintoshes are Complex Instruction Set Computing (CISC) chips. These chips contain a wide variety of instructions that enable the computer to carry out its functions. The much-ballyhooed Intel Pentium is a very fast, highly integrated CISC chip. In that sense, it is a further development of current desktop-computing technology.

Motorola, Apple, and IBM believe that CISC technology has almost reached its performance peak. (Motorola is working on a 68060, however, and DayStar Digital will offer current Mac users a series of accelerators based on it.) Apple sources state that further integration of CISC chips will increase the size and heat output of the chip but provide only a minimal gain in speed. Instead of continuing down the CISC path, the partners decided to tap the power of an alternative chip architecture, Reduced Instruction Set Computing (RISC).

The main difference between CISC and RISC is that instead of the wide variety of instructions contained in a CISC chip, a RISC: chip only contains the instructions used most often. However, it can execute these basic instructions extremely quickly. When complex instructions are required, the RISC chip builds them by combining sets of basic instructions. This means that most operations are handled far more rapidly in RISC than in CISC. (The hardware details of Power PC RISC chips were discussed in the March 1994 "Tech Page.")

Despite his title, Senior Editor Steve O is not an Ancient, nor does he only edit articles written by septuagenarians. He has, however, worked in EM's editorial department longer than any of these young whippersnappers.