Dear Squeak and Blat,

What the heck is this MMX stuff I see in ads about Wintel computers? Is this some kind of Star Wars thing? Is it worth it?

Stevie J. MacWintel

Blat:

Dear Stevie:

No, nothing to do with C3PO or R2D2. The secret to understanding MMX is "symmetric multiprocessing", or "SMP" for short. A growing trend is for personal computers to have more than one processor. Adding more cheaper somewhat slower processors to a PC is often more cost-effective than replacing an existing single processor with a faster one.

"Multiprocessing" is the ability of the operating system to make use of these multiple processors. The Mac OS supports multiprocessing, but only if programs are specially written to use them. This is called "asymmetric multiprocessing". Intel's "MMX" technology is similar - there's an extra processor, but only programs that are specially written to use it can benefit from it (http://developer.intel.com/design/MMX/INDEX.HTM).

In "symmetric" multiprocessing, the OS takes care of making use of the extra processor(s) transparently, without any special programming required. One of the big selling points of the Be OS is that it was designed from the ground up to support SMP, and it does it very well. Windows NT also supports SMP. The new "Rhapsody" operating system for Mac will also support SMP. I can't wait to see the results of new operating systems on music processing!

Hey Squeak, did I get this right? Can you tell them about the Intel MMX chip?

Squeak:

Stevie, Blat was getting awfully technical over there! You should hear him explain how the spit value works on his new Bach Strad trumpet (of course, I'm still playing my old Selmer-Center-Tone technology). Blat gave you a good conceptual overview of multiprocessing. Let me focus on the current MMX chip that is on the market now, the Pentium MMX. There will be more to come for other PCs and even perhaps the Macintosh. In the computer ads in my Sunday paper the Wintel machines were listed as 200 mHz Pentium with MMX Technology or 200 mHz ADM-K6 MMX enhanced processors.

Every computer has a central processing unit or chip called the CPU: this is the brain center of the computer. The Mac has the PowerPC chip in many different flavors; PCs run on different CPU chips, with the Intel Pentium chip one of the more common ones today. The Pentium MMX is just another CPU but one especially made for folks like us who want to do multimedia. Its a multimedia CPU.

Every CPU has a small vocabulary or instruction set of action that it can do. The more instructions the more complex operations it can do and, often times, the faster the complex operations can run. MMX Intel chips have added a whole new set of instructions to the vocabulary for doing sound, and video, and graphics (57 new ones to be exact). This means that the computer can do these things a lot faster. With a CPU without MMX the software has to tell the CPU to do a bunch of things, say, to change the size of a graphic image. But using the new graphic instructions in the MMX chip, this might to done with one or two simple and very fast steps.

The key question is, has the software (for example, Photoshop for graphic imaging or Sound Forge for digital audio editing) been programmed to take advantage of these new features? Probably not yet, but soon. The software development cycle takes time to catch up with new hardware.

The MMX CPU has also added special instructions for telling the computer to do one thing many times. This happens a lot with audio, video, and graphics. You want the computer to go through an entire sound sample and reduce the amplitude by 50% for example. These new commands are like the drum major telling the marching band to do an "about face" rather than telling each member of the band, individually, to turn around.

Another feature of MMX CPUs is the amount of memory that is available right on the CPU. The special memory is call a memory "cache". In the old days a cache was a place where you hid or stored food to use later in the winter or on your return trip from the wildeness; stuff Davey Crockett used to do. On computers it is a special memory place for the CPU to keep the most recent things it just did, so it can get them back quickly should your software need to do those instructions again. The bigger the CPU cache, the quicker the CPU can do those instructions again. The MMX CPU has a much bigger cache than older CPUs.

So when software finally catches up with MMX what will you see? Your current music digital audio and graphics software will do really fancy stuff a lot faster. Desktop video will also get better, better by a lot. This is one application that doesn't work too well over modem lines and the Internet. Videoconferencing that uses the MMX technology will provide greatly improved video delivery quality. It also means that you will be able to do better and better digital video and audio on your computer without special add-on hardware boards. The computer itself with its MMX chip technology will be able to do the intensive computation it takes to capture video and audio without special help.

Start watching for those software ads that say MMX enhanced or that note the more general SMP technology that Blat discussed! Now having offered all that hype, let me say that spending money on this new technology is not for everyone. I purchased a Pentium MMX because I do lots of multimedia and thought that I'd see software of this genre take advantage of the features. But, if you mainly do word processing, music notation, web and email, you may not see any performance gain for several years if at all. Operating system for the Mac and for Windows 95 are still one or more generations away from fully taking advantage of this technology.