Not only has Intel busted through the 3GHz barrier with the latest edition of its Pentium 4 family, but it has incorporated a new performance boosting technology called Hyper-Threading. Does this new technology really deliver on its promises?
It's not about the gigahertz--this seems to be the message we're hearing more and more these days. AMD has been trying to get this idea across for some time with its True Performance Initiative. Transmeta has been saying this since day one about its family of Crusoe processors. And with the imminent public release of its new, designed-from-the-ground-up mobile processor, code-named Banias, even Intel has been hinting hard that there's more to CPU performance than just clock speed.
So how is one to react to Intel's 3.06GHz Pentium 4 processor? Not long ago, you'd be considered certifiable if you suggested that mainstream desktop computers would one day have 3GHz processors in them. I still fondly recall my Atari 800, with its 1.79MHz 8-bit 6502 processor, 48K of RAM, and external tape drive. Anybody out there remember Star Raiders?
A processor that runs at 3GHz is unprecedented--but there's more. Not only is the CPU faster than a speeding bullet, it includes a performance- enhancing technology called Hyper-Threading. The simple explanation of Hyper-Threading technology is that it allows a processor to take advantage of idle CPU resources by working on more than one task simultaneously, resulting in a boost to CPU performance. For the full score on Hyper-Threading and the detailed results of our Labs' extensive Hyper-Threading testing, our "Inside Intel's 3GHz Pentium 4 with Hyper-Threading" feature will be appearing shortly.
Believe it or not, Intel's decision to debut Hyper-Threading technology with the 3GHz P4 should be firmly planted in the "it's not about the gigahertz" camp. It is becoming increasingly difficult to squeeze more power out of CPUs by simply raising clock speeds. Such performance gains potentially increase the CPU-die size and power consumption--and an increase in clock speed never delivers quite the same return in performance. Short of shipping every desktop computer with a liquid-cooled heat sink, what is a CPU manufacturer to do? The answer is to integrate new technologies into the processors that boost performance without necessarily having to boost the clock speed. Intel is setting the stage for a whole new processor performance paradigm.
But does it work?
OK, but does Hyper-Threading actually work? After spending way too many hours in Labs these last few weeks with a Hyper-Threading-enabled system, a myriad of test scripts, a stopwatch in each hand (one of the stopwatches was unceremoniously sacrificed in a moment of benchmarking frustration), and a dwindling prescription for Zoloft, I can report that Hyper-Threading works--but only with the right combination of applications. Just because a system supports Hyper-Threading doesn't necessarily mean that you will automatically see performance gains.
Hyper-Threading boosts the performance of applications that are either multithreaded or multitasking. Very few of today's mainstream apps are multithreaded, so the best chance you have of seeing performance benefits from a Hyper-Threading-enabled system is with multitasking applications. And by multitasking, I don't mean surfing the Web while your e-mail program checks for new messages every 15 minutes. I mean playing a hard-core 3D game while you're ripping music from a CD or capturing a fresh stream of video from your DV camcorder while also encoding a timeline at a high data rate from the movie you just edited.
If our tests showed anything, it's that you can't predict which combination of applications will offer significant performance boosts. We even discovered a couple of circumstances where a few applications actually performed slower under Hyper-Threading. News.com recently reported that several manufacturers, such as Dell and HP, have been shipping their Xeon-based workstations with Hyper-Threading disabled because there aren't enough applications on the market to take advantage of the technology. This makes industry wonks wonder if system vendors will ship their 3GHz P4 desktops to customers with Hyper-Threading disabled as well. (Editor's note: Dell has just announced that customers can specify if they want HT turned off or on at time of purchase. Users can also turn it on or off in the BIOS setup of the PC.)
Should you care?
Consistent and significant performance benefits from Hyper-Threading might not be seen for some time. It all depends on when and if mainstream apps start showing up with multithreaded support. In fact, Intel states that while applications optimized for multithreading will reap a performance benefit from Hyper-Threading, apps that are specifically optimized for Hyper- Threading will benefit even more. So does that make Hyper-Threading the chicken or the egg? For the most part, you will see either no or modest performance gains, depending on how much true multitasking your applications are doing. Should you disable Hyper-Threading if your system supports it? No, leave it enabled, as you are more likely to see performance benefits than you are to see performance degradation.
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