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by Beverly Rosenbaum |
MMX (which doesn't stand for anything) is the first enhancement to the x86 instruction set in more than a decade. Intel added 57 new instructions to its Pentium CPU, doubled the primary cache to 32K, and jammed 36 percent more transistors into the chip.
The MMX instruction set will produce more calculations for each clock cycle of the processor.
In other words, these instructions reduce complex operations to a single step, targeting specific tasks such as audio and video playback and graphics handling.
For example, the current Pentium chip processes only one pixel of an image at a time. But the MMX instruction set bundles eight pixels together and processes them as one.
The result is an eightfold performance gain in screen redraws. In addition, portions of applications with MMX code should run 1.5 to 5 times faster. Intel believes that MMX opens the door for developers to add surround-sound audio, high-resolution graphics, and full-motion video and animation to virtually every aspect of computing.
While applications must be recompiled to take advantage of this prowess, you won't have to wait to benefit from it. The double-size cache of the MMX Pentium — code named P55C — alone will deliver a modest 5 to 20 percent performance boost to virtually any application you already have on your hard drive. This lets more operations execute without using slower secondary cache or main system memory and improves overall processing efficiency.
Of course, MMX is not without its critics — especially where 3-D is concerned. Developers are quick to point out that MMX CPUs cannot simultaneously use the new instruction set and the Pentium's internal Floating Point Unit (FPU), because, to add these capabilities into the existing Pentium die size, Intel had to make a few compromises. The time lost in switching between these two could actually slow certain chores, 3-D images chief among them. Intel officials counter that most multimedia instructions don't use the FPU, and that developers will have to take this design constraint into consideration. Intel is confident that switching time between the MMX instruction set and the FPU on the Pentium Pro MMX should be six times faster than on the Pentium MMX anyway. Other analysts say this shouldn't be a big problem, since few PC applications use the FPU much. But a handful of applications that switch frequently between floating-point and MMX operations could actually run slower on MMX Pentiums than on non-MMX Pentiums of the same clock speed.
Multimedia applications that have been optimized for MMX show far greater speed benefits, though PC World tests failed to confirm Intel's claims of up to 400 percent improvement in some image editing operations. Their tests showed a 50 percent boost for Adobe's Photoshop rewritten for MMX. Macromedia Director results improved by about 35 percent, and there were improvements of just over 20 percent for Fractal Design's Ray Dream 3D Studio.
According to a Creative Labs White Paper, the Myth of MMX replacing the sound card or chip is simply unfounded. MMX, when not being utilized for graphics and video capabilities, has been said to be able to provide certain baseline wave-table music synthesis functions. However, even for this baseline synthesis functionality, users will still need a sound card or sound chip to play legacy music contents and other sound effects. Moreover, this baseline wave-table music synthesis today is a low cost item and the quality of the MMX music will not be able to match the advanced dedicated music synthesis of today's audio products.
Should you buy a system with an MMX Pentium CPU? Before long, you may not have a choice. All of Intel's post-Pentium CPUs will incorporate MMX technology, so the next PC you buy will most certainly feature this technology. Over the next year, buyers will face a mixed bag of Pentium CPUs as Intel phases out non-MMX processors. Many system vendors, for example, will sell Pentium-166 and Pentium-200 PCs in both MMX and non-MMX flavors; expect similar overlap for P-150 notebooks. Meanwhile, MMX Pentiums will appeal to power users and to game and multimedia fans.
Intel's competitors, AMD and Cyrix, also plan to introduce MMX-enabled CPUs this year. Cyrix's code-compatible version of the technology will appear on its M2 chip the first half of this year. Cyrix revealed that their M2 chip modification will expand the primary cache to 64K, optimizing performance on 16-bit and 32-bit code, while incorporating MMX compatibility. And AMD has cross-licensed MMX from Intel, planning to incorporate it in their K6 chip purchased from NextGen last year. Its new chip will also include a 64K primary cache. It will, like Cyrix's chip, support advanced features such as out-of-order execution, which will allow a processor to reorder the execution of instructions so that they can be processed most efficiently. AMD and Cyrix say they'll make their next-generation CPUs pin-compatible with the Pentium socket, but will but target their chips against Intel's Pentium Pro.
But will you like it? According to various independent tests, the modest boost in today's productivity applications won't make you eager to lay out big bucks for the privilege of owning one. Fortunately, this isn't necessary — the price premium for an MMX-powered system will be modest.
Along with the larger cache and beefed-up instructions, the new Pentiums pack 4.5 million transistors — up from 3.3 million in the standard Pentium without affecting compatibility with existing peripherals. MMX Pentiums' lower power requirements should reduce overheating — common in crowded CPUs. But the low voltage means MMX Pentiums won't work on old motherboards, and systems will also need an updated BIOS. Intel promises to introduce MMX Pentium OverDrive chips for existing upgradable motherboards by midyear.
As the first MMX systems arrive, the catalog of recompiled software programs has mostly consumer titles, including a variety of action-packed 3-D video games that beg for big monitors and booming sound systems.
Twelve software companies have MMX applications commercially available.
These include: Adobe, Storm Technologies, Books That Work, Byron Preiss Multimedia Co. Inc., Davidson and Associates Inc., DK Multimedia, Fenris Wolf, Imagination Pilots Entertainment, Maris Multimedia, UbiSoft Entertainment Inc., Yamaha Corp. and Motorola Information Systems Group.
Specially written programs that will take full advantage of MMX are expected later in the year. Users will also enjoy some MMX advantages even in applications that don't specifically support the technology. Many Windows-based programs access multimedia functions through standard Windows modules, such as the DirectX drivers or ActiveMovie player. Microsoft has added MMX capability to these modules, which means existing software that uses them can run significantly faster on MMX systems. For example, video and animation playback in PowerPoint presentations can use MMX technology immediately, even though PowerPoint has not been optimized for MMX. By the time all is said and done, though, MMX will be everywhere.
Beverly Rosenbaum is a HAL-PC member.
E-mail me at webmaster@hal-pc.org with any comments you have and tell me what you want to see here.
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