MMX Power for Desktop PCs

Stretching the envelope, MMX PCx marry a compelling mix of performance and promise.

BYTE Editors

The invention of the microprocessor changed the world and ushered in an era of continually rising expectations. As we moved from the 8088 to the 286 and 386, we assumed that each new microprocessor generation would run faster and deliver better performance. We believed that improvements in microprocessors would continue to be fueled by increasing clock speeds, improving cache management, and optimizing architecture.

Recently, however, the microprocessor industry has had to confront cold, hard reality. The introduction of new CPUs that differ little -- if any -- from their immediate predecessors has left the market confused. As a result, the evolution of the x86 microprocessor is showing the first signs of slowing.

Intel's introduction of multimedia extensions (MMX) is the first major expansion of the x86 instruction set since the 386, and it makes a bold statement: CISC computers are alive and well. The 57 new MMX instructions perform multiple mathematical operations on sets of multiple data items simultaneously. The potential result is powerful programs that can do more, do it faster, and use fewer instructions.

Intel designed the MMX instructions with multimedia applications in mind. MMX should find its greatest use in the bit- and byte-oriented algorithms typically employed in audio and video compression and decompression, image processing, and rendering.

Surprisingly, Intel chose to debut MMX not in its high-end Pentium Pro, but in its established (and more profitable) line of P entium processors. Despite its obvious advantages for business applications, Intel is promoting MMX with a marketing campaign that is decidedly consumer-oriented.

A Wide Field

There's no shortage of manufacturers eager to sell you an MMX PC. For this Lab Report, we gathered 10 systems from eight vendors. We asked them to provide desktop systems powered by a 200-MHz MMX Pentium processor. We also received a 233-MHz MMX Pentium system and a 200-MHz AMD K6 system. All systems had 32 MB of RAM and ran Windows 95. Also mandatory was a 12-speed or faster internal CD-ROM drive, a PCI video adapter with 4 MB of memory, and a 3-GB hard drive.

System prices (not including a monitor) ranged from $1750 to a pricey $2949. Sound cards, modems, Zip drives, and other extra equipment were neither required nor explicitly tested.

Because they were configured similarly and built around identical CPUs (except for the K6 system), it should come as no surprise that these systems turn ed in roughly similar performance. Each is well suited for the role of office or home PC. Therefore, to distinguish these systems, we also evaluated features and usability, including the quality and quantity of the documentation.

Systems from three established vendors are notably absent. Hewlett-Packard declined to submit a system, claiming our testing emphasizes system performance too heavily when assigning an overall rating. IBM begged off, explaining that it had no PCs suitable for this product category. Compaq said its MMX Pentium system would not be ready in time.

The Market

The technology and performance of microprocessors and intelligent subsystems have far outpaced the needs of OSes and applications. An animated cursor or audio clip embedded in a Word document may provide a momentary thrill, but they hardly require a 200-MHz Pentium. So who needs MMX?

If most of your computing involves standard Windows 95 applications, you'll be disappointed with the MMX Pentium. Compared to a standard Pentium running at the same clock speed, you'll see only a fractional performance improvement -- about 10 percent to 20 percent. This is attributable solely to the MMX Pentium's larger on-chip L1 cache (up from 16 KB to 32 KB). You'll be hard-pressed to justify a new MMX system for such a small gain.

Currently, neither Windows 95 nor any standard office application has been rewritten to take advantage of the MMX instructions. Even if these applications were retooled, the percentage of their code that would realize a significant performance improvement is minor. Office applications, despite being loaded with multimedia-like fluff, run just fine on non-MMX Pentium systems.

The first serious applications to target MMX are those with intensive graphics calculations, such as Adobe Photoshop and PhotoDeluxe, Kai's Power Goo, and Vream's WIRL Virtual Reality Modeling Language (VRML) browser. If graphics manipulation and rendering are a major part of your work load, MMX-enabled PCs and applica tions may deliver serious productivity improvements. Also, 3-D game developers will appreciate MMX.

The Upgrade Conundrum

There's not yet a compelling reason to replace your current PC with an MMX Pentium system. If you're shopping for a new PC or a long-overdue upgrade, however, consider MMX seriously. The price difference between the older Pentium and the newer MMX is typically only a few hundred dollars. Substitute an AMD K6, and the price difference almost disappears. Even if your applications can't take advantage of MMX directly, you'll benefit from the increased cache and other architecture improvements.

Intel plans to incorporate the new MMX instructions into all its future CPUs. However, the classic Pentium and Pentium Pro microprocessors -- soon to be replaced by the Pentium II -- will remain strong sellers into the near future.

Given the enormous installed base of non-MMX machines, it is virtually certain that all popular software will be available in non-MMX versions for the foreseeable future. Ultimately, it will be the applications-software developers who will decide if MMX becomes a niche or mainstream technology.

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Contributors

Dorothy Hudson , Project Manager/NSTL

Robert Hummel , freelance writer/BYTE

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The Power of MMX

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