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To maintain the onward march of CPU performance, and keep Moore's famous Law on track, Intel is ditching the pursuit of ever faster clock speeds in favour of multiple processor cores.
A new era for desktop CPUs has arrived with the introduction of the dual-core processor. Although AMD was the first to officially state that it will make the jump to dual core for desktops, the first dual-core desktop processors you'll see from PC manufacturers will have Intel's name on them. Earlier this year, Intel announced that desktop processors using dual-core technology will be available by the end of June, but the company recently hinted at March's Intel Developer Forum (IDF) that dual-core processors could be available even sooner than that.
What is dual core?
Simply put, dual-core technology places two independent execution units onto the same processor die -- think of it as two processors in one. This idea differs from Intel's HyperThreading (HT) technology, which uses a single (physical) execution unit but allows the processor to run two separate (logical) execution threads. Some of the dual-core processors will also include HT, so there will be some dual-core CPUs that support four independent threads (two of the threads are running on physical execution units, and two are running on logical units).
It turns out that dual core is just the first step; soon, we'll see even more multiple cores on a single processor die. Intel predicts that we'll see up to eight threads per desktop processor by the end of the decade (and up to 32 threads per server processor). It's becoming increasingly challenging to continue driving the clock speeds up, so developers are seeking out new ways to increase processor capabilities. In his keynote address at IDF, Intel's soon-to-retire CEO Craig Barrett equated moving to multiple cores as the most logical way to keep up with Moore's Law:
"If you want to have transistor budgets in the billion or 10 billion range, you have to do things a little bit different to continue to double the processing capability, the processing power, on an annual basis. In fact, going to dual core, multi-core approaches are the way you would do that. You more or less throttle the clock-speed increases, but you're able to continue to use more and more transistors and more and more processing elements--cores--to bring forward great capability. That enables all sorts of new applications and allows us to continue the basic premise of Moore's Law: innovate and integrate. In this case, part of the innovation is taking a core and then being able to integrate many of those cores into a device."
Making it work
In order for dual-core technology to be adequately utilised, however, the operating system and the applications need to support thread-level parallelism -- which basically means running multiple execution threads simultaneously. According to Intel, Microsoft's Windows XP and more than 200 applications, including Adobe's Photoshop CS and Roxio's VideoWave 7.0, are multithreaded.
Most of today's multithreaded applications are of the content-creation ilk, which tend to perform many operations in parallel. As dual-core technology becomes more prevalent, you can expect to see more multithreaded programs become commonplace -- for example, 3D-intensive games can take advantage of dual-core technology by using more robust physics and AI engines for more realistic effects and gameplay. But since Windows XP itself is multithreaded, you don't necessarily have to be running multithreaded applications to see a performance gain. Windows is a multitasking environment, and as such, there are usually applications running in both the foreground (such as the browser you are using to read this) and the background (such real-time virus scanning). A dual-core processor can execute the multiple threads of these applications more efficiently.
Intel claims that it saw performance gains of between 50 and 124 percent from a dual-core-based system over one using a 3.73GHz Pentium 4 Extreme Edition on its own multimedia application tests. For more mainstream programs, Intel estimates about a 40 percent performance improvement. As soon as we get our hands on a dual-core processor, we'll put it through its paces to see whether it delivers on the hype.
Making its debut
The first dual-core processors we'll see from Intel will be for high-end desktops. One will be a Pentium 4 Processor Extreme Edition. It will feature two 3.2GHz execution units -- each of which includes 1MB of L2 cache and supports HT -- for a total of 2MB of L2 cache and support for four execution threads. The CPU will operate on an 800MHz frontside bus (FSB) and will include Intel's new 64-bit Extended Memory 64 Technology (EM64T) and eXecute Disable (XD) bit functionality. The 206mm² die will be built on Intel's 90nm process technology and will include a whopping 230 million transistors. Intel will continue to use the LGA775 package, but the new chip will not work in motherboards that use older chipsets.
The new chipset for the dual-core Extreme Edition will be the 955X Express chipset. It will support both 800MHz and 1,066MHz FSB speeds, 667MHz dual-channel DDR2 memory, and up to 24 PCI Express lanes. Additionally, the 955X will support dual x16 PCI Express slots. Intel has been reticent about the specific details of these dual PCI Express slots, but the rumour mill has been speculating that, because of Intel and Nvidia's cross-licensing agreement, the new chipset will support Nvidia's SLI (Scalable Link Interface) solution, which allows you to run two 3D graphics cards simultaneously.
The other dual-core CPU we'll see soon from Intel will be the 3.2GHz Pentium D. The Pentium D is almost identical to the dual-core Extreme Edition -- even down to the same number of transistors. The only significant difference is that the Pentium D will not support HyperThreading, so this CPU supports only two threads. The Pentium D is meant to be paired with the upcoming 945 Express chipset.
Waiting in the wings
Intel's initial intent is to aim dual-core processor directly at the high-end performance market; the company will continue to manufacturer and market single-core processors for mainstream and budget customers. However, Intel predicts that by the end of 2006, dual-core processors will have sufficiently infiltrated mainstream systems to the extent that roughly 70 percent of all desktops and notebooks shipped will use dual-core CPUs.
Intel also expects to move over to a 65nm manufacturing process next year. On the desktop front we'll see the single-core Cedar Mill processor and the dual-core Presler CPU. Presler will feature two Cedar Mill cores on a single die, with 2MB of L2 cache on each core, for a total of 4MB of L2 cache.
Dual-core won't arrive on the mobile front from Intel until 2006, when the company releases its 65nm, dual-core mobile processor Yonah -- with 2MB of L2 cache that will be shared by the two cores. Yonah will be part of Intel's next update to the Centrino platform, currently code-named Napa. Napa will consist of the Yonah processor, the Calistoga chipset with integrated graphics, and the Golan Wi-Fi chip. Golan will support 802.11a, b and g, but it is not slated to support the yet-to-be-approved 802.11n specification. Intel also claims that even though Yonah represents a significant increase in the number of transistors on the CPU die, the battery life will be at least as good as it is with the current Centrino platform.
Now that Intel has launched the first true dual-core salvo, it remains to be seen how its arch-rival AMD responds. But even more important, will dual-core technology live up to expectations? Check back with us soon -- after we've tested dual-core's capabilities and reported on its performance.
http://reviews.zdnet.co.uk/hardware/processorsmemory/0,39024015,39191512,00.htm
Intresting.
