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Double Your Pleasure
with a Multiprocessor Box
by Scot Hacker |
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Also by Scot Hacker:
Hardware/Software Buyer's Guide
Database-to-Web Tutorial
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If you've been keeping an eye on the consumer hardware market, you've probably noticed a growing phenomenon — the availability of computers with either two or four processors. Isn't one processor person per person enough already? Just how fast do these demons go, anyway?
The answer to the growing technical debate over the benefits of dual-proc machines, ironically enough, is two-pronged: While the notion of multiple processors makes good sense in theory, the world is saddled with outdated operating systems that don't take full advantage of them... that is, if they even recognize them at all.
| "Lots of cheap chips on a system that knows how to take advantage of them will beat the pants off any season's latest and greatest single CPU." |
On one hand, I think it's safe to say that the popularity of single-processor machines will begin to wane in the next 18 months, and within five years, multi-CPU motherboards will become the norm. The public's greed for speed is seemingly insatiable. If the industry can't increase clock speeds quickly enough to satisfy gamers, programmers, and multimedia "prosumers," the obvious solution is to simply toss a few more CPUs into the box and make them work together. Sounds great, until you realize that adding a second CPU will not, in the vast majority of cases, double your speed. In fact, you may actually see very few speed gains at all.
The problem is that in order to take advantage of all that extra horsepower, your operating system and your applications must be capable of evenly and efficiently distributing the task load across all available processors in a process called Symmetric MultiProcessing, or SMP —a mouthful that's actually easier to say than to pull off well.
Because SMP works at the lowest level of the system, doing it right requires advance planning on behalf of the operating system vendor — it's not something you can easily ship in an upgrade with next year's release. The core of MacOS and Windows were built more than two decades ago, when SMP was the last thing on engineers minds. As a result, neither Windows 95/98 nor MacOS speak SMP natively, and the speed increases seen by users of those systems are going to be pretty minimal. It is, however, possible to build support for multiple processors into applications themselves, and there does exist a cross-section of software that will let your computer kick that second CPU into high gear. Unfortunately, most of that software is available only to high-end graphics and design markets, not the general consumer.
On the other hand, Windows NT 4.0 does take advantage of multiple CPUs, and the forthcoming MacOS X (formerly known as Rhapsody) also plans to support SMP. However, MacOS X isn't due out until late 1999, while Mac users have been promised SMP for a very long time. Since MacOS X is based on NeXTStep's "Mach" kernel, which has done SMP for quite some time, SMP is a safe bet in MacOS' future. Users of Linux, the free variant of Unix that runs on PCs, also enjoy SMP today, as do the dwindling numbers of OS/2 users. However, the SMP implementations in NT, Linux, and OS/2 aren't quite as elegant or as efficient as they could be, and none of them will double your speed automatically. In general use, measured over the long run, 60% — 80% performance increases are about all these users can expect.
Where are the rest of those clock cycles going? Straight out the window. The mere act of managing multiple processors and juggling all the data that moves between your memory, disk, video card, and CPUs, all across a system bus that's showing its age faster than today's processors, while laboring under the literally millions of lines of system code that's accreted over the past 20 years, is a monster of a task. In addition, while both NT and Linux are capable of breaking jobs into small tasks called "threads" for smoother distribution, neither system is pervasively multithreaded, so the granularity of the task-bits aren't as smooth as they could be.
Still, there's a profound logic in the basic notion of SMP. Look at how quickly chip prices drop after being first introduced. Sometimes they fall to half their introductory price in just a matter of months, and to a small fraction of the original cost withinin a year. That means you can get two of last year's 266 MHz chips for less than the cost of today's fastest 400 MHz beast, and still come out financially ahead. Take it a step further, and think how cheaply you could pick up four 233's — you'd have more than 900 MHz of raw speed and still pay less than your neighbor who just spent a month's earning's on the latest and greatest.
And if you had an operating system that could take full advantage of every clock cycle you threw at all those chips, you really would have close to 900 MHz, not just a portion thereof. Lots of cheap chips on a system that knows how to take advantage of them will beat the pants off any season's latest and greatest single CPU.
Actually, there is one operating system that pulls this trick off quite nicely. It's called BeOS, from Be, Inc. If you haven't heard of the system yet, you will soon, as the company is rapidly picking up steam now that their system runs on both Intel-based machines and PowerMacs. BeOS has SMP running through its DNA, and will milk all of your processors for practically all they're worth, achieving around 90% speed increases for each additional CPU... with no theoretical limit on the number of CPUs it can handle. What's more, BeOS developers don't have to write special applications to take advantage of Be's SMP capabilities — it all happens automatically. The system is young, so there aren't a ton of applications available for it yet, but that's changing quickly. Most importantly, the system isn't bogged down by 20-year-old design constraints. Read more about the BeOS here and here.
If you're not quite in the mood to go installing alternative operating systems, the new multi-processor machines you're seeing advertised probably aren't going to do you a whole lot of good right now. On the other hand, if you're geeky enough to appreciate NT, Linux, or BeOS, you stand to gain a great deal. And all of this technology will become more commonplace over the next few years, as our operating systems learn to speak SMP more fluently and our motherboards grow fatter pipes. Buckle up.
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By day Scot Hacker (yes, that's his real name) is a Ziff Davis techno-weenie, but by night, he's a goateed motorcyle-riding poet. Or is it the other way around? Check out his funkadelic Web site, The Birdhouse Arts Collective.
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