06-20-2002, 09:31 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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XScale and the Pocket PC – what’s going on?
With all the anticipation over the Intel XScale processor running at 400 MHz, expectations were high that any Pocket PC would double in speed. You double the MHz from 206 to 400 and the Pocket PC should get twice as fast, right? Not exactly. There are many issues that relate to overall device speed, not the least of which is software. Ed Suwanjindar from the Microsoft Mobile Devices group responded to my questions via email on this issue. I'll post my own thoughts on this issue under a separate entry. On to the Q&A!
THOUGHTS: Early reports based on those who own the Toshiba e740 Pocket PC 2002 device are telling us that XScale at 400 MHz performs slower than a StrongARM at 206 MHz on some tasks. This came as a surprise to many people.
SUWANJINDAR: “We are aware that PXA250 (XScale)-based devices are not demonstrating the huge performance gains that were anticipated. That said, Pocket PCs continue to offer the best performance and the richest functionality vs. other handhelds on the market today.”
THOUGHTS: I’ve seen a few articles on line saying it's Microsoft's fault for not having an optimized OS in place for the XScale launch. What is Microsoft’s response to this?
SUWANJINDAR: “Our software remains the same. This is the same Pocket PC 2002 software that performs fabulously across other ARM processors (StrongARM 1110, OMAP710, etc). We made a hard decision several years ago to move away from supporting several processor architectures and target a single core. This was a difficult decision that we think ultimately benefited our OEMs, developers and customers by unifying our platform around single processor architecture -- ARM V4. The PXA250 utilizes the ARM V5 instruction set with backwards compatibility for ARM V4. When we completed the Pocket PC 2002 software in June 2002, we optimized for the most broadly compatible processor core available at the time (ARM V4), which it still remains today. Choosing to support one processor core ensures we don’t fragment our platform for developers and cause extra work for our ISVs to optimize their applications each time a new processor technology is released.
By staying with ARM V4 architecture we assure longer life spans for our customers existing hardware – for instance if we were to move to an ARM V5 architecture we would have to obsolete the all SA1110 iPAQ devices. Protecting the investments of our developers and customers is very important to us. To that end we’ve worked to make our devices upgradeable. Moving to ARM V5 would break upgrade compatibility. We’re not prepared to strand an installed base of over 2 million iPAQ users.”
THOUGHTS: Some industry analysts have said that Microsoft doesn't have any fix in place because Intel couldn't get the chips out in time.
SUWANJINDAR: “We have implemented and released specific software changes that our hardware partners are implementing without breaking compatibility for our OEMs and users. While we believe there may be incremental gains that could be had via small optimizations we are not convinced there are across the board improvements that would amount to any kind of dramatic system wide speed up. We have to develop software based on the processor architecture that offers the broadest compatibility for developers and when we shipped Pocket PC 2002 as it still is today, that was ARM V4.”
THOUGHTS: Some of those same analysts have said it will be 2004 until there's an OS that can use the XScale CPU properly. Is that an accurate estimate?
SUWANJINDAR: “It’s too early to talk about the next version of our software. That said, we’re committed to delivering best-in-class functionality and performance while providing a foundation that enables our developer community to continue to innovate and build successful businesses on our platform.
Microsoft considers mobile devices a strategic business. We are committed to working closely with Intel and other silicon vendors on delivering future versions of our Pocket PC and Smartphone devices. We have released specific software modifications to our OEMs that in total are all of the optimizations we believe are possible to maximize PXA250 performance (without causing incompatibilities for our OEMs and developers).”
THOUGHTS: This isn’t a good story for the Pocket PC and as more XScale devices hit the market, the issue will get more obvious and ultimately become more serious.
SUWANJINDAR: “Agreed, this isn’t a good story. Very simply, we think this is one of those times when the technical reality didn’t measure up to market expectations. That said for people who use these products, this isn’t a big deal. I’ve used both of the new XScale products that are out there (new Toshiba and iPAQ). They offer the same type of performance that I’ve come to expect on a Pocket PC. I think the market expectation of what performance on a 400 MHz processor vs. 206 MHz processor has been unreasonable. In the mobile device space, we don’t think that MHz is what ultimately matters to customers. What matters the most in this market is whether customers can do what they want to do with devices quickly and easily. With the richest set of software applications built into any PDA on the market, and the strong momentum that Pocket PC has with developers writing for our platform, we think that customers will be able to do the things they want to do with the performance they expect on devices using PXA250 processors.”
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