The Coming War: ARM versus x86

Conclusion
The ARM Cortex-A8 achieves surprisingly competitive performance across many integer-based benchmarks while consuming power at levels far below the most energy miserly x86 CPU, the Intel Atom. In fact, the ARM Cortex-A8 matched or even beat the Intel Atom N450 across a significant number of our integer-based tests, especially when compensating for the Atom’s 25 percent clock speed advantage.

However, the ARM Cortex-A8 sample that we tested in the form of the Freescale i.MX515 lived in an ecosystem that was not competitive with the x86 rivals in this comparison. The video subsystem is very limited. Memory support is a very slow 32-bit, DDR2-200MHz.

Languishing across all of the JavaScript benchmarks, the ARM Cortex-A8 was only one-third to one-half as fast as the x86 competition. However, this might partially be a result of the very slow memory subsystem that burdened the ARM core.

More troubling is the unacceptably poor double-precision floating-point throughput of the ARM Cortex-A8. While floating-point performance isn’t important to all tasks and is certainly not as important as integer performance, it cannot be ignored if ARM wants its products to successfully migrate upwards into traditional x86-dominated market spaces.

However, newer ARM-based products like the NVIDIA Tegra 2 address many of the performance deficiencies of the Freescale i.MX515. Incorporating two ARM Cortex-A9 cores [more specifically, two ARM Cortex-A9 MPCore processors], a vastly more powerful GPU and support for DDR2-667 [although still constrained to 32-bit access], the Tegra 2 will doubtlessly prove to be highly performance competitive with the Intel Atom, at least on integer-based tests. Regarding the Cortex-A8’s biggest weakness, ARM representatives told us its successor, the Cortex-A9, "has substantially improved floating-point performance." NVIDIA’s CUDA will eventually also help boost floating-point processing speed on certain chores.

Unmatched software support has always been the "ace in the hole" for the x86 contingent. However, with the success of Linux and the maturity of its underlying and critical GNU development toolset, Linux/GNU support could be the great equalizer that allows ARM to finally overcome the x86 stranglehold in netbooks and even notebooks and desktops. Maturing Linux support might also assist ARM chips to make further incursions into gaming devices.

I didn’t expect it, but the emerging war between ARM and x86 microprocessors is turning out to be much more competitive and interesting than I ever imagined.

In addition to the main ARM versus x86 focus of this report, there is also a subplot pitting the new Intel Atom N450 against the new VIA Nano L3050. The Intel Atom N450 is a remarkable product in that it is the first x86 SoC [system-on-chip] that is suitable for smartphones and other ultra-low power environments. As such, the Atom promises to dramatically improve the sophistication and performance levels of those market spaces.

While the various Atom models currently dominate the booming netbook market, it is evident from our JavaScript tests that the VIA Nano L3050 is much more desirable if JavaScript performance is important at all. Across our JavaScript benchmark results, the 800MHz VIA Nano L3050 is about 50 percent faster than the 1GHz Intel Atom N450.

However, VIA still lags Intel in terms of suitability for low power consumption environments, largely because Intel leverages its outstanding 45nm fabrication technologies with the Atom, while VIA still produces the Nano L3050 in the relatively elderly 65nm Fujitisu process node. The Atom is also strong on multithreaded tasks as demonstrated by its CoreMark victory. Hyper-Threading will also benefit Atom in I/O intensive environments where the single-core Nano will be hard-pressed to keep up.

Lastly, the AMD Mobile Athlon in this comparison gives us important insight into how the new chips from Intel, VIA and ARM stack up historically. Overall, across all of our performance tests, the ancient Barton core-based Athlon came in a very close second behind the VIA Nano L3050. This suggests AMD could easily produce a competitive low power CPU if the chipmaker did nothing else but shrink one of its older core designs while adding a few power saving tweaks.

In summary, ARM is positioned very well to engage in battles with the Intel Atom as that x86 chip advances into smartphones. The ARM Cortex-A8 appears to use much less power than the Atom, while often delivering comparable integer performance. Nevertheless, the Atom is significantly faster overall when considering holistic system performance, but that performance will be accompanied with a battery life penalty and significantly more heat production. Heat is a serious problem within the tight confines of mobile phones.

New chips based upon ARM Cortex-A9 derivatives, like the NVIDIA Tegra 2, address many of the performance weaknesses we encountered with the Freescale i.MX515. If ARM is to achieve sustained victories in the netbook space - let alone in the more performance demanding notebook and desktop spaces - ARM must substantially improve floating-point thoughput.

While the dedicated functional block approach used by ARM and its legions of licensees to provide image manipulation, video decoding/encoding, security and Java acceleration is still valid, it is not a substitute for double-precision floating-point performance.

ARM representatives told us for this report that the Cortex-A9 "has substantially improved floating-point performance."  It will take a big jump forward to catch their x86 rivals, but if ARM pulls it off, Intel, AMD and VIA are going to have a big, bloody war on their hands. It is conceivable the x86 empire might finally see the boundaries of its swelling, vast territories begin to retract in the near future under an army ant-like assault of tiny, fast, cheap, multi-core ARM microprocessors coming at them from dozens of different companies.

ARM’s success might also have a negative impact on Microsoft, since Linux will almost certainly play a major role in ARM’s ability to storm the netbook, "nettop," notebook and even desktop spaces.

Whatever the outcome, it’s time to pay attention to ARM. Our results clearly demonstrate how it was possible for an ARM chip to steal the Apple iPad away from Intel’s Atom. The Apple iPad might represent merely the first of many ARM victories in its escalating war against the x86 world.


Final Notes
We thank Katie Traut and Phillipe Robin from ARM for the impressively tiny but full featured Freescale i.MX515-powered Pegatron prototype Ubuntu system. We also thank C.J. Holthaus and Glenn Henry from Centaur Technology for the VIA Nano L3050 reference board.


About the author
Van Smith is currently working in his own company called Cossatot Analytics Laboratories. Van was head of benchmarking for Centaur and represented VIA Technologies within the BAPCo benchmark consortium. Van has written a number of computer benchmarks including OpenSourceMark and miniBench and he has influenced or directly contributed to many others. For instance, Van wrote the cryptography tests in SiSoftware Sandra.

Nearly ten years ago, Van departed Tom's Hardware Guide as Senior Editor to form his own website, Van's Hardware Journal [VHJ]. Van was recently interviewed and quoted in a CNN article based upon his investigative journalism published at VHJ. Van also served as Senior Analyst for InQuest Market Research.

On Bright Side of News*, we have the privilege of having Van as our resident expert on microprocessing architectures and work on developing unified benchmarking solutions so that you, our dear readers - can get fair apple-to-apple comparisons even if at first, it doesn't look possible to do a side-by-side comparison.