Under the hood: an inside tour of the Pentium 4

Collectively dubbed Intel NetBurst microarchitecture, the new elements are meant to push more low-level programming instructions through the chip's electronic pipelines. This avoids the bottlenecks and other restraints that will likely cap the clock speeds achievable with the PIII's older design at around 1.3 GHz.

Kevin Krewell, senior analyst at MicroDesign Resources, says NetBurst's design is meant to speed up apps that send data in bursts, such as streaming media, MP3 playback, and video compression. "The design is a change in emphasis from typical integer performance [as in standard business apps] to media performance," he says.

Transistors doubled for speed

Intel uses what it calls Hyper Pipelined Technology in the P4, which doubles the depth of transistors that process the electronic on/off bits making up the CPU's program instructions, so more instructions can be worked on at a time. Another feature, Advanced Dynamic Execution, keeps up to three times more instructions in the pipeline than the PIII can and makes educated guesses about which instruction branch to process. ADE acts like a chef's helper who doesn't know the exact recipe but tries to assist by fetching anticipated items. But speculative execution can hinder the chip if the system guesses wrong, says Nathan Brookwood, principal analyst at Insight 64. Such branch mispredictions are more common with office apps, he says.

Intel increased the speed of the system bus to 400 MHz, compared to 133 MHz in the fastest PIIIs. To ensure that instructions don't back up while travelling from memory to CPU, the new Execution Trace Cache holds already decoded instructions while others finish. A so-called double-pumped arithmetic logic unit runs twice as fast as the rest of the CPU, quickly calculating integer (whole-number) math. It, along with the higher clock speed, ought to speed up all applications, including word processors and spreadsheets.

Speedier web service

Finally, the P4 introduces Streaming SIMD Extensions 2 (SSE2) -- 144 new multimedia and graphics instructions designed to speed up various applications. For example, some SSE2 instructions improve processing of speech, video, image editing, and encryption -- all the rich Web content Intel says the P4 is born to run. However, until programmers write software to take advantage of these instructions, you won't see performance improvements. Intel touts a short but impressive list of upcoming SSE2 programs, including Shiny Entertainment's Sacrifice game, Dragon Systems' Dragon NaturallySpeaking, and Macromedia's Dreamweaver. More important, Intel says Microsoft will add SSE2 support to its DirectX 8 driver, the lingua franca of Windows graphics.

Analysts are reserving judgment on P4's performance vis-à-vis its current rival, AMD's 1.2-GHz Athlon paired with DDR SDRAM.

"They've come up with an architecture that clearly allows them to scale the clock rate," says Brookwood. "The challenge for Intel is to demonstrate that the clock-rate superiority translates into performance superiority."

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

David Essex

PC World
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Tom Pope

Dynabook Portégé X30L-G

Ultimately this laptop has achieved everything I would hope for in a laptop for work, while fitting that into a form factor and weight that is remarkable.

Tom Sellers

MSI P65

This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang

MSI GT76

It really doesn’t get more “gaming laptop” than this.

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?