Multicore Mania

This article is part 1 of a two-part series; part 2 will appear on Friday, December 16.

When you can’t make a microprocessor run faster, what do you do? You combine two or more microprocessor cores, of course.

Intel and AMD, the top industry rivals, have already introduced dual-core chips for desktop PCs. And that’s just the start of a trend that could bring an important change to PCs: multicore processing. Both of these leading chipmakers hope to pack four cores into desktop PC chips by 2007. And Intel researchers are investigating how to put tens or even hundreds of cores onto a single chip.

Both chipmakers and PC makers need multicore chips for an important reason: they’ve run out of performance headroom on existing designs. (For years, chipmakers have added transistors and ratcheted up clock speeds to make processors run faster. But clock speeds can be increased only so much before a chip radiates too much heat inside the PC case.)

But why does the average PC user need two, four, or eight cores on a chip? For starters, think multitasking. “I call multitasking the silent ‘killer app’,” says Shane Rau, program manager for semiconductor research at market-research firm IDC. “Today, all the apps we’re using are nickel-and-diming the processor to death.”

Most individual applications already run well – on their own. But, as any Windows user knows, running multiple programs simultaneously, say, a word processor, audio player, and anti-virus software, will eventually make the unwanted hourglass appear. Multicore processing could end that waiting period.

Furthermore, given today’s ever-changing security threats, multitasking requirements will only go up, say industry observers. Most people will continue to use more applications simultaneously, while PCs will need to run more security programs in the background just to protect themselves.

In particular, streaming audio and video tasks can hog microprocessor resources. Intel believes multiple cores will be much better at tasks such as downloading video from a PC to a personal media player. And Intel’s upcoming multicore processors run cooler than the originals – which could lead to innovative notebook and desktop PC case designs. The company’s dual-core chip, nicknamed “Yonah,” is set to debut in early 2006.

At the International Consumer Electronics Show in Las Vegas next month, Taiwanese PC maker AOpen plans to demonstrate a Yonah-powered machine about the size of Apple’s Mac mini-desktop computer, which measures 17 centimeters wide, 17 centimeters deep, and 5 centimeters tall. Yonah played a big role in Apple’s recent decision to buy Intel chips, according to Kevin Krewell, editor-in-chief of In-Stat’s Microprocessor Report, because Yonah will enable faster Powerbook notebooks.

First-Round Mistakes

Early dual-core chips, such as Intel’s Pentium D, got mixed reviews – mainly because their performance gains were unimpressive when running software designed for traditional single-core processors. To really tap into the power of dual-core, or multicore chips, software applications need to be written or rewritten to take advantage of two or more cores, a process called multithreading.

Programmers have already built multithreading into Windows XP, Linux, and the Mac OS X operating systems, so they can throw the power of one CPU at system background tasks and the other CPU at, for instance, a demanding application such as displaying video. On the other hand, many application vendors, including game makers, haven’t revised their applications yet.

“We have multi-threaded software in scalable server applications today, but it is rarer in client applications” for desktop computers, Krewell says. “Adobe has embraced multithreading for content creation software, including Adobe Photoshop; but most other application software companies haven’t done so yet.”

Also, this first round of chips – including AMD’s Athlon 64 X2 Dual-Core and Intel’s Pentium D – still produce more heat than designers would like. That forces the dual cores to ratchet themselves down at times and run at less than their potential top clock speeds. So, in fact, gamers and other users of high-intensity applications are often wise to use a PC based on a powerful single-core chip like AMD’s Athlon 64 FX.

A larger wave of multithreaded applications will arrive when Microsoft’s Windows Vista operating system ships in fall 2006, IDC’s Rau says.

Just as importantly, the next generation of Intel dual-core chips will draw less power – keeping their cool without compromise. Code-named “Conroe” for desktops, “Merom” for notebooks, and “Woodcrest” for servers, these chips should also debut in fall 2006.

Eight is Enough?

Multicore designs will be the dominant microprocessor trend for this decade and beyond, according to both Intel and AMD. By 2007, both companies plan to offer quad-core microprocessors for consumer desktop PCs. And Intel could introduce eight-core chips as soon as 2008, some analysts predict.

“You have to time the introduction of the hardware with the software,” says Phil Hester, AMD’s chief technology officer. “Going to two cores is a pretty good answer for many apps today.”

As AMD plans its future chips, including quad-core, it must balance chip production costs and software benefits. For instance, a chip with three cores and a large amount of cache memory may deliver more bang for the buck than a four-core chip, Hester says. That’s because many applications, including demanding ones like Adobe Photoshop, make use of cache memory to speed up tasks. “It may make more sense for us to spend on fewer cores and include more cache,” Hester says.

Another possibility that might give users of multicore machines a big performance payback is specialized cores designed to excel at certain tasks, say, graphics, Web browsing, or security tasks. “You might have one core running your XML stream while another does the standard PC work,” Hester says, mentioning that AMD is investigating this kind of design.

Fitting more cores into a microprocessor, however, is just the start of the design challenges that hardware and software companies will face in the era of multithreading. The fastest processor in the world will still wait around if a system’s main memory can’t keep pace with it. And this problem will grow if a chip has hundreds of cores.

Coming tomorrow: We take a closer look at the hardware and software challenges with multiple cores. What hurdles must be overcome before multicore processing can deliver on its promise?

Laurianne McLaughlin is a technology writer based in the Boston area.