MMX: Marketing Hype, or Innovative Technology?

So, if you're thinking of buying a new PC, is a Pentium MMX worth the extra cost? Or should you wait instead for the next generation of MMX (the Pentium II Processor)?

by Tina Lieu

In January, Intel officially announced the release of its MMX-technology Pentium processor (the Pentium MMX) in Japan. Touted as the most significant advance since development of the i386 chip, Intel's Pentium MMX announcement stoked the Japanese media and public interest to a fever pitch.

Against a backdrop of falling PC prices and depressed sales, buyer anticipation of new model PCs incorporating the MMX technology contributed to stranding Japan's PC vendors on top of worrisome high inventories. Faced with the task of selling off their non-MMX PC models while the new Pentium MMX machines were coming out put PC vendors in a no-win situation.

Lots of hardware, little software

In Japan, the official release of the Pentium MMX came almost simultaneously with announcements of Pentium MMX-equipped PCs by Dell Computer, Digital Equipment Corporation Japan, Gateway 2000 Japan, Hitachi, IBM Japan, Sanyo, Seiko Epson, and Toshiba. These front runners were quickly joined by NEC and Fujitsu, and other makers soon jumped on the bandwagon. The first wave of Pentium MMX PCs hit the Japanese market from late January to early February.

What effect are Pentium MMX computers having on the PC market? According to Katsushi Shiga, analyst at Dataquest (of the Gartner Group), "MMX technology will have a big impact. It enlarges the range of multimedia applications and widens the spectrum of users. [By enabling less powerful machines] to run applications like Adobe's Photoshop or Macromedia's Director, MMX will eventually allow more users to take advantage of this software. And in business, video conferencing will become a more common and casual affair."

Shiga dismisses the claim that MMX technology will enable Windows to erode the Macintosh's traditionally strong areas of DTP and multimedia. "Rather than steal share from the Mac, the MMX will enlarge the number of PC users using multimedia."

"The MMX chip will gradually drop in price into the latter half of 1997. By the end of 1997, probably almost all new PCs on the market will be loaded with MMX. And MMX-optimized software will likely be bundled in those machines, thus further spreading the use of MMX and stimulating software developers to write software using MMX," says Shiga. He cautions, however, that "the software will take more time than the hardware to reach the market. It's rather hard to write software for MMX [and] adapting existing software to take advantage of MMX will be almost like rewriting it from the beginning. Software used by professionals, such as Photoshop 4.0, will be MMX-optimized first; software for amateur use will probably not become widespread until the fourth quarter of '97."

This is a point to bear in mind if you're in the market for a new computer. MMX technology instructions are only effective if you have software that is written to take advantage of them.

What's new?

The MMX Technology Pentium Processor is not so much a new MPU (microprocessor unit) as one that incorporates additional instructions and functions to improve the processor's efficiency and performance. The Pentium and Pentium Pro are highly complex chips, and making them more complicated would be extremely difficult without significantly raising the costs of the chip. So Intel instead went back and simplified the instructions, adding four significant functions to the conventional Pentium processor.

First, Intel added a whopping 57 new instructions to the MPU. This new instruction set simplifies the work of the MPU and enables it to perform the same functions with fewer instructions. One example is the algorithms that take the inner product of vectors (a basic calculation needed for processing images, sound, and video); MMX technology reduces the instructions that need to be executed from 40 to just 13.

A second advance is implementation of "simple instruction multiple data" (SIMD), through which a single set of instructions can be applied to multiple data items. This enables data to be processed more efficiently and quickly in parallel (at the same time). Multimedia data processing involves a lot of time-consuming, computer-intensive loops, and running a bunch of them at the same time is more efficient.

-Home users targeted-

As mentioned in the article, Japanese PC makers were quick to announce Pentium MMX-loaded PCs after the Intel announcement. A survey of the PCs available as of mid-February at the MMX Convention in Tokyo showed that very few systems were marketed with a business focus; most of the desktop models had multimedia extras and were targeted for home use. Loaded with a DVD (digital versatile disc) player were Panasonic's Woody CF-200PDX with PD drive (DVD optional), Toshiba's Brezza 5200VMB (with an easy-to-use push button panel), and NEC's Cereb (with remote control, widescreen TV monitor, and wireless keyboard). IBM's Aptiva S-series B80, B85, and B95 models come with a joystick, and Mitsubishi's Apricot MS660 has an easy-to-use remote control.

Before MMX, for example, a register (a place in the MPU to hold data for processing) could only hold one pixel or audio byte per cycle. With SIMD, four to eight pixels can be operated on simultaneously in a 64-bit register. Where a conventional Pentium might only be able to show every fourth frame during video playback, MMX technology allows every frame to be shown, making for smoother viewing.

Third, the Pentium MMX chip has a larger cache (32K rather than 16K). This larger cache alone improves the processing speed of any application (not just MMX-optimized applications) by 10% to 20%.

The fourth advance is improved "branch prediction" efficiency. As Michael Aymar, vice president and general manager of Intel Corporation's Desktop Products Group, explains, "In the past, data had to go through a loop before being branched [sent] off on its way. Now, based on where other data was sent, the processor will prepare the data for a certain path before processing it [which] is efficient if the same operation is repeated." Since with multimedia data there are many repeated operations, this function can greatly improve performance.

How a processor runs

How do these advances make the Pentium MMX better? To put it simply, a computer's CPU talks with all the different parts of the computer. The CPU receives data, performs necessary operations (such as "add 2 to the value of each pixel"), and sends the new data back out, all the while making sure that the parts run in sync.

Like an electronic conductor, the CPU beats time by sending out regular, electrical clock signals, each equal to one cycle. Since each instruction takes one or more clock cycles, a chip that has more clock cycles per second can execute more commands. The clock speed of chips is counted in megahertz (MHz; one million cycles per second). Thus a 133-MHz chip runs through 133 million cycles per second, whereas a faster 150-MHz chip runs through 150 million cycles per second. One of MMX's advances is that many of its instructions take only one clock cycle to complete, thus streamlining processing and speeding up performance.

Another variable that determines the performance of a processor is its number of registers (the memory segments where it stores the data it is about to work on). A processor with more registers can process more data per clock cycle.

For storing data, cache size is also important. To use a rough analogy, a processor fetching data from the hard disk is like flying from Japan to the US to get a book. The processor fetching data from RAM is like going to the local library, while the processor getting data from an on-chip cache is like reaching over to your bookshelf.

Pentium MMX vs. PowerPC

Compared to a conventional Pentium processor of the same clock speed, a Pentium MMX processor yields higher performance (with MMX-optimized software, much higher). But how does the Pentium MMX compare with other chips, such as the PowerPC processor produced by Motorola and used by Mac compatibles? Pentium chips are based on CISC (Complex Instruction Set Computing) architecture; PowerPC chips are based on RISC (Reduced Instruction Set Computing) architecture. One of the advantages that MMX technology brings to the Pentium chip is single-cycle instructions, something that is inherent to RISC architecture. According to Gary Montgomery, operations manager of Nippon Motorola Ltd.'s RISC/NetComm Operations, RISC means that instructions are single-cycle, or pipelined to single-cycle instructions. All instructions are 32 bits long, and the CPU issues new instructions every clock cycle.

The number of registers is one important variable that determines how quickly and well a chip perform, but, as Montgomery explains, "Once the number of registers in a chip is decided, it is very hard to change that number without also changing the architecture. When the PowerPC architecture was first designed, Motorola had the foresight to put in 32 registers, each double-precision 64 bits. That means a decimal with the accuracy of 26 places will fit in a register." And thanks to "register renaming," the PowerPC actually has more than 32 registers at its disposal (although the 32 are the only ones that programmers need to worry about).

Pentium chips, on the other hand, have only four 64-bit registers. While MMX technology is able to create four more "virtual registers" when running MMX instructions, only four registers are available for non-MMX processing.

Montgomery explains in a simplified way how register renaming works. Suppose that different instructions are being called to perform operations on two different kinds of data (C and D). Both data may use register A, but they can't be in the same register at the same time. The CPU, therefore, takes data C and stores it in register A. It then stores data D in a shadow register called Register A1, and leaves a note to itself about data D's real location.

Although the computer will still send an instruction to perform an operation on data D in register A, the CPU will say, "The data that you really want to call for this instruction is in register A1" and get the proper data. All this happens transparently without loss of processing speed. So, in essence, there are more than 32 registers in a PowerPC because of this register renaming function.

Intel's Pentium MMX has the same number of registers as the conventional Pentium: four registers of 64 bits each. When MMX technology uses these four registers, it creates four more "virtual registers." But floating point operations and MMX operations cannot share a register. So when data C is needed for an operation, it is put into the register; then, if data D needs to be operated on, the CPU takes out data C and puts in data D to perform the operation. When the other instruction gets there and wants to use data C, the CPU retrieves data C and puts it back into the register a very time-consuming process.

For MMX 3D graphics processing as in games movement of polygons (i.e., figures) requires floating-point operations, but painting the polygons requires MMX instructions. Since floating point operations and MMX operations cannot share a register, the MPU must switch back and forth between registers for the two operations. This explains why 3D graphic performance is still relatively weak in the current version of MMX.

Asked what he thinks of Intel's Pentium MMX, Motorola's Montgomery laughs. "It's a marketing coup for Intel! MMX is just trying to do what the PowerPC already does. If you want to know what MMX is aiming for, look at a Macintosh."

Byte Magazine reported ("MMX: Better in Fits and Starts," February 1997) on a performance comparison test between a 200-MHz Pentium MMX, 200-MHz Pentium Pro, and 200-MHz PowerPC 604e running Adobe Photoshop 4.0, an MMX-optimized application. In five tests of common Photoshop functions, the PowerPC 604e beat the Pentium MMX in three of the five functions considered to be the most important: arbitrary rotate, unsharp mask (custom), and RGB to CMYK.

MMX-optimized software, now and later

Intel sees applications for MMX technology in multimedia-rich home applications such as video, image, and sound processing, and in office uses such as multimedia data on intranets and videoconferencing. MMX is, more than anything, aimed at improving performance of multimedia data; there are few spill-over benefits to programs like word processing and spreadsheets (except for the non-MMX related improvements of cache size and improved branch prediction).

At Tokyo's Intel MMX Technology Convention in February, Microsoft was not yet ready to announce when and how it intended to incorporate MMX technology into its future software releases. Over a dozen software makers were on hand, however, to demonstrate their MMX-optimized software (mostly music-composing programs, games, music videos, and educational CD-ROMs). Almost without exception, the makers said they planned to market products that were MMX-optimized but also playable on conventional Pentium machines.

- Don't try it! -

Can you buy a Pentium MMX chip and slot it into your current machine for a homemade upgrade? Not unless your system has a special motherboard with variable adjustable current. The Pentium MMX chip runs on a power-efficient 2.8 volts rather than the conventional Pentium's 3.3 volts. You'll fry your new Pentium MMX chip if you plug it into a conventional Pentium system's motherboard.

Sega Enterprises, Ltd., was at the convention demonstrating its fast-paced and popular "Cyber Troopers Virtual On," a 3D fighting game (ported from the arcade game version) that requires MMX technology to run. According to Hiroyuki Otaka, manager, of Sega's PC division, "This game would have a very hard time running without MMX technology because it's extremely graphics heavy. It has double the graphics of the most graphics-heavy game currently on the market. This game [being demonstrated] is running on 32MB of RAM, but that's just the minimum. Ideally you'd want even more RAM." Otaka estimates that of the game software produced by Sega each year, about 60 titles are for use with their game console system, Sega Saturn, and only about a dozen titles are for PCs.

Asked about Sega's future plans for MMX-optimized games, Otaka says, "Sega is planning on putting out another ten titles from April that will use MMX technology, but those games will also run on non-MMX machines. Most of those will be 3D." Regarding the future of MMX and games, Otaka said that he'd like to see MMX catch on and spread, and that he hopes to see the Klamath [Intel's next generation of MMX chips] come out soon. He points out, however, that the speed of the CPU is only one of the factors that will improve PC gaming (advanced video cards and more RAM being others).

The next generation

According to an Intel spokesman, the chip formerly code named Klamath is now officially called the Pentium II Processor. In essence, it is a Pentium Pro with MMX technology added. Shipment of the Pentium II is scheduled to begin in the first half of 1997. It is expected to reduce the time-consuming register switching between MMX and floating-point operations, and will incorporate additional instructions that enhance 3D graphics processing plus upwardly new MMX instructions."

On the PowerPC side of the market, Motorola released a 240-MHz 603e chip for notebook computers in second-quarter 1996; the 603e is featured in Apple's new PowerBook 3400c series of notebooks. In February, Motorola released a technical paper on the next-generation chip which, according to Rieko Asanuma of Nippon Motorola Ltd, will be announced later this year. Motorola's Montgomery says this new chip is expected to be up to productions standards by the third quarter of this year, and systems based on the chip are expected by year end.

And the playing field is growing. Exponential Technology of San Jose, California has announced a microprocessor based on the PowerPC architecture that will run at 533 MHz. It is expected to be released in 1997.

Will the likely proliferation of MMX-required software spark another cycle of PC buying similar to the launch of Windows 95? Time will tell, but the next year or so looks to be an exciting time for the chip industry.

Please note that this table is provided asmerely a sampling of MMX Pentium machines on the Japanese market and that new models are continually being added and discontinued (some as quickly as three months after release!). If you are serious about purchasing a machine, contact companies and dealers directly for the latest information. Note that in the listing of CD-ROM drive speed, some companies list average speed whereas other list maximum speed. Computers are listed by manufacturer in alphabetical order.

*All CPUs listed are Intel's MMX Technology Pentium Processors

TFT= thin film transistor (i.e. active matrix LCD screen)

MMX-Equipped Notebook/Portable PCs (Table A)

Company

Compaq

DEC

Epson

(or DVD-ROM drive)