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Saturday, July 31, 2010

Intel Pentium 4 Vs. Atom: A Battle Of The Generations

Intel Pentium 4 Vs. Atom: A Battle Of The Generations

Most people know that Intel’s Atom is a slow, low-cost processor. But does it even offer enough performance to take it beyond desktop processors nearly a decade old? Today we're comparing a modern Atom CPU to two Northwood-class Pentium 4-based PCs.
We were sorting out some old hardware in one of our test labs and wondered what to do with our old Socket 478 Pentium 4 gear. Disposing of it doesn’t feel quite right, and we know that many Pentium 4 systems remain in service. Clock speeds between 2 GHz and 3.4 GHz still provide sufficient performance for a home server or backup PC, so why not put up two different Pentium 4 systems against single-core and dual-core Atom solutions to see how today’s low-cost computing solutions hold up?

Convenience Computing
We done several articles dealing with Atom and comparing its performance and efficiency with other solutions. First and foremost, it’s important to note that Atom is not in the same market segment as desktop-oriented Core 2, Core ix, Phenom, or Athlon processors. Atoms enable the lowest-cost netbooks and nettop computers. They aren’t meant to be particularly efficient, and they won’t satisfy a power user. Any entry-level Core i3 desktop will provide many times better power efficiency, in fact.
Atom makes sense where local computing performance doesn’t matter very much: browsing the Internet, communicating via email or social networks, and processing documents and spreadsheets. For these, Atom is more than enough.
Buy Atom or Recycle P4?
Does it make more sense to purchase a cheap Atom-based computer or to recycle and/or continue to use an existing Pentium 4 machine? Both run at decent clock speeds and come with 512 KB of L2 cache. Both can be considered above average if you have modest performance expectations. And both have a comparable transistor count: 55 million for the Pentium 4 (based on the Northwood design) and 47 millions for the Atom 230.
More importantly, you might be able to get an older P4 system for very little money from a friend or business upgrading to newer hardware. We compare the Atom 230 and D510 to a Pentium 4 (Northwood) 2.2 and 3.2 GHz.
Oldie But Goldie: Intel Pentium 4 (Northwood)

The Northwood-based Pentium 4 was the first processor to employ Intel’s Socket 478 interface and dual-channel memory. It was the second Pentium 4 generation, and it utilized a 130 nm CMOS manufacturing process with 512 KB of L2 cache and clock speeds between 1.6 and 3.4 GHz. Early versions were based on a 400 MHz front-side bus speed (100 MHz) while faster models ran at 800 MT/s (200 MHz) and used dual-channel DDR-400 memory. 

The step to an 800 MT/s FSB and the 865/875 Express chipsets brought substantial change. Intel introduced its LGA 775 interface and the 90 nm Prescott core in 2003, but since these chips increased power consumption without introducing an equivalent performance increase, we decided to stay with the older platform for this review.
First, we tested a Pentium 4 at 2.2 GHz. This is a 400 MT/s FSB design that didn’t support Hyper-Threading. In order to get the comparison numbers with HT, we also added a Pentium 4 C at 3.2 GHz. Hyper-Threading is valuable bcause the operating system perceives two processing cores for every physical core. The technique is better at saturating the Northwood’s long, 20-stage pipeline. The 3.2 GHz model runs on an 800 MT/s FSB with a maximum TDP of 89 W, while the 2.2 GHz model stays below 57.1 W.
Obviously, the 3.2 GHz version is much faster, but it also drains significantly more power at idle and under heavy loads. Keep in mind that processors in 2002 did not have power saving mechanisms like SpeedStep. As a result, both Pentium 4 systems require at least twice the idle power than our Atom solutions and up to five times the peak power. Will the Pentium 4 system be capable of delivering performance in about the same range?
DFI’s LANParty Pro 875B with an ATI Radeon 800 Pro served for this project.

Better Than Its Reputation? Intel's Atom

Atom 230
The Atom 230, also known as Diamondville, was Intel’s first Atom generation. It comes with clock speeds of up to 1.6 GHz and a 133 MHz front-side bus. It also supports Hyper-Threading, like the Pentium 4, and has the same 512 KB of L2 cache. But this is all they really have in common.
While the Pentium 4s we used are 130 nm products, the Atom uses Intel’s 45 nm process. The limited clock speed paired with the modern manufacturing process helps the single-core chip to stay within a thermal envelope of only 4 W. Unfortunately, the whole Atom platform doesn’t necessarily save power, since Atom 230 typically pairs with the terribly inefficient 945GC. Still, if you only look at the CPU, Atom does really well.

A direct comparison between the Pentium 4 and the Atom 230 at 1.6 GHz reveals little in common. The Atom 230 significantly trails the Pentium 4 in some tests, while it stays fairly even with the Pentium 4 2.2 GHz in others. The MP3 encoder Lame runs much faster on the Pentium 4 systems. So do Adobe Acrobat, iTunes, and WinZip. However, the 1.6 GHz Atom 230 actually does better than a Pentium 4 2.2 GHz in 7-Zip and Adobe Photoshop CS4, and it’s not too far behind in HandBrake and MainConcept, although the overall results are awfully slow on both platforms. Still, the Atom supports more advanced SSE instructions, which may explain a part of the results.
Atom D510

The second-gen Atom D510 is a dual-core part based on the Pineville core. It’s based on the same execution core as the first-generation Atom, which is why it doesn’t really deliver more performance per clock than Diamondville. The new CPU is rated at a 13 W TDP, which looks like a lot more than the initial Atom’s 4 W. However, Atom D510 includes a more advanced graphics engine and memory controller, making the northbridge obsolete. This clearly helps the latest Atom reduce overall platform power consumption by going from three chips to two.
The CPU runs at a similar clock speed as before, now 1.66 GHz with a 133 MHz quad-pumped front-side bus. The two cores still support 64-bit operation and Hyper-Threading, which means that the operating system can access four logical processing cores.