Intel calls software makers to rally round XScale

Intel says that faster performance will arrive gradually for the new XScale Pocket PCs, but that the burden is on software developers

Intel says that software developers will bear the burden of boosting performance on newer models of Pocket PC handhelds, as manufacturers move from Intel's StrongARM SA1110 processor to a new Intel architecture called XScale.

The shift to the new processors has created confusion for users in the weeks since the first XScale-based devices appeared on the market, as the newer devices -- all running on a 400MHz PXA250 chip -- appeared to deliver about the same performance as older 206MHz SA1110-based handhelds, despite the increase in clock speed.

Earlier this week Microsoft admitted that the performance problems were due to a mismatch between the Pocket PC software, optimised for StrongARM, and the XScale-based PXA250. The PXA250 is based on the ARM V5 instruction set, but Pocket PC is optimised for ARM V4, according to Microsoft.

In addition, Microsoft said it is unlikely to optimise Pocket PC for ARM V5, as this would either make previous versions of Pocket PC obsolete, or require Microsoft to maintain two separate versions of the software. Microsoft did say it is working with hardware vendors to make some minor tweaks to Pocket PC for XScale, but did not expect this to substantially improve performance.

Intel, however, says that it will be a simple matter for software makers to release new versions of their software optimised for XScale, without needing optimised Pocket PC software and without running the risk of fragmenting their software.

Intel compared the process to the introduction of any new architecture, including the Pentium 4. "Optimised software that takes full advantage of the XScale microarchitecture will occur over a period of time, like any new processor microarchitecture transition," said Intel representative Mark Miller.

Intel is persuading software makers to use its Integrated Performance Primitives, which simplify the process of optimising software for a particular processor. Several vendors, including Microsoft (with Windows Media Player), Macromedia, Real Networks and video decoder maker Packet Video, have said they will optimise for XScale.

These optimisations will be the key to higher performance, according to Miller, with internal benchmarks showing as much as 20 to 60 percent performance improvements. The optimisations are specific to XScale and not to ARM V5, he said.

In addition, while StrongARM had topped out at 206MHz, PXA250 will be able to scale to much higher speeds, according to Intel. The company has demonstrated an XScale chip running at 1GHz.

However, Intel's strategy could also bolster the chipmaker's dominance in the Pocket PC market. Last year Microsoft shifted the platform exclusively to the ARM architecture, with the expectation that device manufacturers could use ARM-based chips from any chipmaker. However, such devices would not be able to take advantage of the performance enhancements of applications optimised for XScale.

Other chipmakers, including Texas Instruments and Motorola, also make ARM-based processors for handheld computers; Palm, for example, has partnered with TI, Motorola and Intel for its next-generation, ARM-based PDAs. But only Intel-based Pocket PCs have made an impact on the market since the introduction of Pocket PC 2002 last year.

With most Pocket PC makers planning to shift to XScale, Intel says it expects the architecture to become the Pocket PC industry standard. "From our experience, the software industry will port for the highest volume products in the market, which to date has been the Intel StrongARM processor in the PDA space," Miller said. "Consistent with any microprocessor microarchitecture change, we expect that most future applications will be optimised around the new XScale microarchitecture."

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