And I Thought the Salsa Was Hot!

Sep 1, 2003 12:00 PM, By Oliver Masciarotte


Education Guide

Mix is gearing up to present its longstanding annual Audio Education Guide in its November 2014 issue. Want to have your school listed in the directory, or do you need to update your current directory listing? Add an image, program description, or a logo to your listing! Get your school in the Mix Education Guide 2014.

Chips, they're everywhere: in your toaster, in your car (quite a few, in fact) and, of course, in your DAW. This month, we begin a two-part series to revisit the age-old PPC vs. Intel debate and look into the new 64-bit crop of CPUs, which will have a significant impact on host-based DAWs.

To go forward, we must go into the past! Yes, cast your mind back to last March, when “Bitstream” discussed single- vs. double-precision DSP processing. If you recall, run-of-the-mill DSPs typically store numbers as a floating-point, 24-bit mantissa and an 8-bit exponent. Some fancy-pants DAWs double up the data and perform double-precision calculations, with a 48-bit mantissa and a 16-bit exponent. This larger number of significant digits allows more signal processing to be performed before rounding errors are introduced.

Okay, fair enough. But to generalize, most arithmetic processes are more precise with double the word length, including the general-purpose CPUs that are the soul of Win and Mac computers. In Windows world, those general-purpose Intel CPUs we take for granted began their evolution as the 4004, introduced in 1971. The 4-bit 4004 wasn't much fun, but its children — the 8-bit 8008 (introduced the following year) and the 8080 (in 1974) — paved the way for the 8086, which, it could be argued, spawned the whole personal computer industry. The 8086 ran its 16-bit words at a blazing 5 MHz, could address a fat 1 MB of memory and formed the computing core of IBM's first PC. MITS' Altair, the first personal computer, used an 8080 and came to market in 1975 for $395. Notice the trend: 4, 8 and then 16-bit computers. By the mid-'80s, Intel had a 32-bit processor: the 386.

By the early '90s, Intel was working on the first Pentium, and users of the other common flavor of microprocessors — Motorola's MC68000 Series — realized that they also needed a next-generation shot in the arm in order to compete. In 1991, Motorola, IBM and Apple Computer formed the PowerPC (PPC) Alliance, and so the PPC's RISCy ying to Intel's CISCy yang was born. Though the first product of the PPC Alliance, the 601, was a 32-bit microprocessor, it had both 32- and 64-bit registers and a 64-bit FPU (Floating Point Unit).

Four years later, the PPC Alliance released the second-generation 620. With 64-bit internal data paths and 32-bit I/O, it was the first (though partial) 64-bit implementation of the PowerPC architecture and set the stage for things to come. In a very smart move, the PPC family was designed as a 64-bit cruncher with backward binary-compatibility for 32-bit applications. It would take awhile for Intel to learn the backward-compatibility lesson, but, with the ability to chop its spectacular profit margins and still make a tidy penny on its CPUs, Intel countered the PPC threat with lower prices, while starting a dizzying spiral of ever-increasing clock rates to compensate for inherent CISC performance limitations.

A big physical difference between the PPC and the Pentium is the PPC's Reduced Instruction Set Computing (RISC) character. Relative to CISC (Complex Instruction Set Computers), like the original Pentium, RISC architecture — with fewer instructions baked into silicon — sacrifices complexity for increased speed: the lean and mean approach. Another factor, according to IBM, was that “…the Power Architecture was unique among the [six] existing RISC architectures in that it was functionally partitioned, separating the functions of program flow control, fixed-point computation and floating-point computation.” The architecture's partitioning facilitated the implementation of a “superscalar design,” a now-ubiquitous feature, which made it possible to execute multiple instructions during a single clock cycle. Intel, while clinging to its x86 architecture, has its own superscalar family called the i960, which is used for embedded application and not general-purpose computers like the Pentium. Not to be outdone by the competition, the Pentium has increasingly cribbed pages from its i960 brother, adding a RISC core with CISC trimmings to make it backward-compatible with older x86 processors.

However, during the past decade, there is one metric that CPU powerhouse Intel has emphasized in its saturation ad campaign: Faster is better! Intel latched onto clock speed as the defining selling point for its products. Unfortunately, clock speed alone is a false measure of real-world performance and can only get you so far, because architectural decisions by the Intel design team have forced them to ramp their clock to the limits of heat dissipation in order to improve execution. Indeed, current draw (and subsequent heat generation) is the limiting factor in the go-fast world of Intel. It's not uncommon to find all sorts of exotic cooling methods used by manufacturers and hobbyists to keep their Pentiums from doing a “Three Mile Island” on the motherboard: Heat pipes, active refrigeration (both solid-state Peltier heat pumps and old-school compressed gas versions) and even water cooling has been pressed into service to chill those huge, power-hungry chips.

When asked about the current range of 32-bit Intel processors and how they hold up to current PowerPCs, digital audio pioneer James A. Moorer (now of Adobe Systems) doesn't have any qualms about stating that, “the PPC is light years better and faster than any of the others. The P4 [Pentium 4] is pretty close, but still quite a ways off. The big thing is that the PPC chip has 64-bit data paths, and all of the Pentium chips are 32-bit data paths only. That makes the PPC chip more than twice as fast; it yields more than twice the data rate. Every benchmark I've done comes out with a difference of a factor of four times over the fastest single-processor Intel processor I could find. My benchmark is pure double-precision, floating-point crunch-power, with big, sprawling data structures. My FFT routine [Fast Fourier Transform, the basic math trick that powers all audio DAWs] generally incites the worst-case behavior of most processors' address-prediction hardware.”

Address prediction? The whole PPC vs. Intel debate, in a way, boils down to prediction and how designers go about auguring upcoming processing requests. However, that discussion will have to wait till next month. The stage is set to discuss a chip feature that mainframe, scientific workstation and Apple customers have long enjoyed: 64-bit and longer data words. Longer is better for “sprawling data structures,” and such big-league computing is starting to make an impact on the Windows desktop, as well.

Next month, we'll delve further into the Intel vs. AMD and Itanium vs. Opteron tussle, while looking at IBM's 970, the fifth-generation PowerPC destined for Big Blue's servers and Apple's new PowerMacs.

Drop by for deeper threads and illustrations concerning this month's topic.

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