Five Things You Didn't Know About Dual-Core Processors

Dual core processors have been the subject of so much hype that perceptions about the technology seem to have trumped some of the realities.

Both AMD and Intel have posted Web pages in which they extol the virtues of their respective dual-core devices. That makes timely sense, since most industry watchers agree that 2006 is the year dual-core will become ascendant.

However, hidden in the such venues, and among numerous news stories on the subject, are some surprising and uncommon facts. Accordingly, we bring you five things you probably didn't know about dual core.

Intel and AMD weren't the first to ship dual-core processors.

The widespread assumption is that the dual-core duel has been fought solely on the PC front, with AMD and Intel vying for the title of first to market. That's incorrect.In fact, IBM beat both companies to the multicore punch, albeit with a non-X86, server processor. That occurred when Big Blue rolled out its dual-core Power 4 chip in 2001, for use in IBM's RISC servers, in 2001.AMD and Intel announced their respective dual core plans in 2004 and began their first dual-core shipments in 2005. (Here for AMD, and here for Intel.)

However, there's such a dizzying array of dual-core parts -- including dual-core Opteron server and Athlon 64 desktop chips from AMD and dual-core Pentiums and Xeons from Intel -- that it's hard to keep up with the ongoing blizzard of announcements from both companies.

On the mobile front, IBM is also technically winner of the race to market, with low-power versions of its PowerPC 970FX, unveiled in 2005. However, this is pretty much an OEM product that's not available to the average buyer. Nor is it an x86 part.

In the x86 world, Intel won the mobile dual-core race, with its Centrino Duo, announced in January. The mobile device powers the popular new iMac, notwithstanding the fact that the iMac is a desktop. (Internally, it's designed something like a large notebook computer stuffed into the back of a flat-panel display, as this internal teardown shows.) The new iMac is also the first Apple computer to use an Intel processor.

Dual-core was forced on the industry by technical challenges, not proactively embraced .

The real reason Intel and AMD went with the technique wasn't because dual-core presented itself out of the blue as a brilliant idea. Indeed, chipmakers would have been quite content to push ahead with ever-faster single-core processors. However, that wasn't feasible, because as clock speeds headed north of 3 GHz, single-core processors began to consume too much power.Indeed, in 2005, Intel cancelled a planned 4.0 GHz "Tejas" processor, when it appeared that the chip would dissipate more than 100 Watts.

Along with power, super-fast single-core chips were becoming expensive to cool, requiring bigger heat sinks and more powerful fans to keep them within their operating temperatures.

Enter dual-core processors, which provided a way to continue to improve performance, while essentially putting off for a while having to deal with the dual bugaboos of power consumption and heat. "It was because as a processor vendor, that's the only way we could provide performance within the right power envelope," Margaret Lewis, AMD's director of commercial solutions, told TechWeb.

Of course, strict semiconductor constructionists would want to qualify that with talk about on-chip voltages, the size of the chip's features and other technical factors. (Some advances in these areas actually make keeping the power down more of a challenge.)

In addition, some balk at the idea that dual-core is a panacea. As Linuxhardware.org's June 2005 article, Going In-Depth With Dual Core put it: "From our standpoint dual-core isn’t new; it’s just an old product (Symmetric Multiprocessing) that has been reborn in [a] new skin... The same performance questions about dual processor system over a single processor remain."However, as a simple explanation, it'll largely suffice. "The laws of physics don't change; we just figured out how to give us some more runway," Lewis added.

Dual-core won't necessarily make your computer's clock speed faster, but it will boost your PC's throughout.

Here's a fine technical distinction with a difference. There's nothing inherently faster about dual-core, as compared to a single-core processor. If all you want is raw clock speed, you should buy the fastest processor you can find. The fastest single-core boxed processors from Intel are the 3.8 GHz Pentium 4 model 670 and the 3.6 GHz Pentium 4 model 660. The fastest dual-core available at posting time is the 3.2 GHz Pentium D 840. (A 3.6 dual-core GHz Pentium D 960 is scheduled to be released in the second quarter of 2006.)

On the AMD front, the single/dual- core top speeds are comparable. The single core Athlon 64 3400+ runs at 2.4 GHz. The dual-core Athlon 64 X2 4600+ is also clocked at 2.4 GHz.However, two cores chugging away at 2.4 GHz will obviously outperform a single such core. Even two cores running at a bit less than 2.4 GHz should deliver better throughput than a somewhat faster single-core device.

Perhaps surprisingly, though, it won't double its performance. (That's because of drag cause by resources shared between the two cores.) "What we've seen is anywhere between 1.4 and 1.8 times performance increases, depending on the application," said AMD's Lewis."When you double the number of cores, you keep the same amount of power, but you almost double the throughput," is the way Shekhar Borkar, an Intel Fellow, put it, in a 2004 interview. (Borkar is obviously putting somewhat less significance on the shared-resources loses.)

Many technical sources caveat the performance question by pointing out, as does the Wikipedia, that "multi-core processors require operating system support to make optimal use of the second computing resource."

Simplified, this means that multithreading is the key to good performance. Multithreading has come to the fore over the past few years in single core environments, and it’s being exploited even more aggressively in the cause of dual core. "You run a supercharged multithreaded application every day on your computer; it's called an OS," said AMD's Lewis. "You always had a multithreaded environment. It [dual core] makes that multithreaded environment run more efficiently."

Intel is likewise a multithreading proponent. The chip giant emphasizes that its dual-core products, which supporting its Hyper-Threading Technology "can process four software threads simultaneously by more efficiently using resources that otherwise may sit idle."

For dual-core sophisticates, the caveat here is that there's much debate about how well multi-threading has been realized to date, and how fully existing operating systems and applications are able to take advantage of dual-core processors. (On the OS front, while some Linux distributions support dual core, Windows Vista will be Microsoft's first OS to be designed with dual core in mind.)

Almost half of all PC users are still clueless about dual core.Nearly three years after AMD announced its Opteron, 48 percent of PC users are clueless about just what a dual core processor is, a recent survey conducted by Harris Interactive found. (In the business world, of course, it's a different story. It's widely acknowledged that datacenter managers and CIOs are well aware of the power dual core computing can bring to the enterprise.)

In the survey, which focused on home users, 42 percent of personal computer owners said they are somewhat familiar with dual-core and an early adopter elite of 10 percent swear they know it cold. Of that 52 percent with either some or a lot of awareness of the technology, only 12 percent already have a dual core system.

That scant percentage should increase soon. Market researchers Frost & Sullivan forecast that dual-core processors will replace single-core chips at a 15 percent to 25 percent annual clip, in desktops, notebooks and servers. Intel may be expecting a quicker ramp up -- it plans to ship 60 million dual-core processors in 2006.In a bid to build additional consumer awareness, both Intel and AMD have taken a page from Hollywood. Intel recently hosted a competition, the Intel Indies Film Contest, in which it awarded ViiV PC equipment to what it judged to be the best short digital films. AMD's video tournament is dubbed The 64 Second Film Contest. AMD says the contest shows hold its Athlon 64 X2 processors are "taking content creation and multimedia performance to the next level. While the winners of both contests are well done (the Intel films tell stories, the AMD shorts are more like hip commercials) the entries have little on the face of them that suggests computing, other than the fact that they were likely edited on PCs.

Dual-core isn't the last word on cutting-edge computing.

In a few years' time, dual core may be old hat. Intel is already preparing a four-core server processor for shipment in 2007. AMD is also working on quad-core chips.Further afield, Intel is readying an eight-core device, code-named Yorkfield, for delivery in 2008. AMD is less specific, saying only that it will move to more than two cores in 2007.

On the non-x86 front, Sun is already offering an eight-core server processor in the form of its UltraSparc T1 (formerly Niagara).

Indeed, cores and more cores look to be with use well into the future. "All chips will end up as multiprocessors, and we have to learn how to program them," Simon Davidmann, the founder of Co-Design Automation Inc., told EE Times last fall.