The Desktop Traffic Jam

Multicore chips are a boon for desktop processing speed, but software can't always keep up. Here's why.

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What's needed is not more code, but different code -- and a different way to organize the application, adds Microsoft's Smith. "You must understand parallelism, and that is not always obvious."

A first step is to minimize the use of variables. "Variables are artifacts of sequential execution," Smith says. "If it is always true that A+B=C, what if someone gets in the middle of that and adds something to B so that the equation no longer holds true? You must have a consistent state where that is prevented." Traditionally, this prevention has been done by locking the variables, but Smith advocates the use of transactional memory, which does much the same thing automatically by isolating the variables from other code that's running at the same time.

If the application vendors have been slow to adjust to multicore, the public has not. According to hardware vendors, buyers these days are counting cores instead of gigahertz.

"In the past, people really cared about the frequency of the processor and about making sure they had the latest speed," says Bob Grim, a marketing executive at Advanced Micro Devices Inc. "Now we see them being more concerned about what kind of visual experience they will get."

"Gigahertz used to be the metric for buyers, but now there is tiering," agrees Glenn Jystad, senior manager at PC vendor Acer Inc. "Single-core processors are limited to entry-level systems, while dual-core is a step up, and you really start to realize performance in the quad-core category, which is now mainstream." He predicts that three-core processors, promoted by AMD, will fade away by the end of the year, since there is little price difference between three-core products and the more powerful quad-core systems.

Meanwhile, performance issues aside, vendors favor multicore processors for their ability to help reduce system power consumption. If three heads of a quad-core system have nothing to do, "you can put them to sleep," Turley says. "Being able to throttle back is one of the charming side effects of multicore processing."

"Using multiple cores will let us get more performance while staying within the power envelope," agrees Jystad. "Today's 95-watt Intel quad-core processor is substantially more powerful than the 95-watt Pentiums of three years ago."

Nonetheless, says Intel's Alfs, "Moore's Law continues. We continue to integrate more and more capability onto the processor." But the chief result, he predicts, will be more cores.

Wood is a freelance writer in San Antonio. Contact him at

This version of this story originally appeared in Computerworld's print edition. It's an edited version of an article that first ran on


Copyright © 2009 IDG Communications, Inc.

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