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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06-20-2002, 09:42 PM
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Thinker
Join Date: Jul 2003
Posts: 335
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It thought it was possible to run ARM v5 code on a v4 device
I read somewhere that the new instructions in the ARM v5 core would cause and exception within the processor which would act like an interrupt. Software could then decode the specific instruction (although slower than a v5 core).
This was originally installed (I think) to allow devices with and without a floating point unit, where the missing hardware could be emulated in software with a subsequent performance hit.
I think it's definately in Microsoft's interest to get the PocketPC running full tilt on XScale, otherwise Palm V6 may come along and eat it for breakfast.
Regards,
PJE
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06-20-2002, 09:47 PM
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Contributing Editor Emeritus
Join Date: Aug 2006
Posts: 8,228
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Re: It thought it was possible to run ARM v5 code on a v4 de
Quote:
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Originally Posted by PJE
I think it's definately in Microsoft's interest to get the PocketPC running full tilt on XScale, otherwise Palm V6 may come along and eat it for breakfast.
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I don't think Palm is V5 ready anymore than PPC is. Both are optimized for V4 ARM code. All of Palm's partners are producing ARM V4 chips anyway. They just announced they will run on the X-Scale, but the didn't do anything for that. V5 runs V4, it just runs slow, negating much of the speed gains. 
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06-20-2002, 09:58 PM
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Thinker
Join Date: Jun 2002
Posts: 390
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I don't think that's the kind of answer that I want to hear.
I basically says. Sorry we won't do V5. Optimizing V5 globally won't get us that much faster anyway.
This is the kind of thing PALM Inc. would spew! gargh!
Conclusion: Buy el cheapo SA PPC, they give more bang for the buck.
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06-20-2002, 10:02 PM
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Pontificator
Join Date: Jul 2003
Posts: 1,466
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Sounds like we're screwed. Microsoft has no intention of "optimizing" the OS for xScale.  ops:
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06-20-2002, 10:04 PM
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Ponderer
Join Date: Mar 2002
Posts: 50
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While this story explains why Microsoft was not ready with ARM v5 support, it does not explain the peformance issues. I believe that articles like these dance around the real issues that are holding back performance.
Overall, Intel's decision to continue using a 100 mhz bus for ram and peripherals with a 400 mhz cpu was a step backwards from the 103 mhz bus with a 206 mhz cpu. So until Intel adds support for faster memory access these chips will not perform at a full 400 mhz all the time.
See "Are Pocket PC's Starving?" for a more technical discussion about these issues at http://www.cewindows.net/faqs/pocketpcstaving.htm
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06-20-2002, 10:09 PM
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Ponderer
Join Date: Mar 2004
Posts: 64
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This blows.
Clearly PIM apps etc. won't benefit from the XScale, but can multimedia apps that would stand to gain from increased performance be written to take advantage of XScale, or will the OS prohibit that?
In other words, we know that PPC2002 doesn't and won't take advantage of XScale, but does that mean 3rd party apps can't either? Or can they be written that way at the expense of backwards compatibility?
Anyone?
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06-20-2002, 10:12 PM
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Intellectual
Join Date: Feb 2002
Posts: 209
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Translation:
We forgot to keep the url www.pocketpc.com registered in the middle of a court case involving the product. You think we'd have our sh*@ together enough to make a hardware agnostic OS? Then again, we can't/won't make our own word processing program for PPC2002 work as well as competitors on Palm. Tables? You don't need no stinkin' tables! If that doesn't tell you something.....
That would make too d%$ much sense.
Yep. PPC2002 runs on Xscale. Not worth a crap and in some cases worse than old technology, but it runs........kinda.
Microsoft and the good ole boy network of PDA manufacturers have, effectively, built the largest beta test group ever.
Don't get me wrong. I wouldn't go for the alternative (Palm), but it had to be said.
Thinking..........
Those new Sony clamshell PDA's are nice.
(Smacks himself) SNAP OUT OF IT!
Couldn't MS just insert processor sniffing OS code and let US and the developers choose what we want. Maybe even offer V4 compatibility mode in a V% optimized version of the OS (See windows XP).
I'm babbling now, but it makes sense.........I think.
:?
__________________
And there you are.
I was just thinking, "What could take this headache I have over that edge to a full blown migrane?"
And there you are.
- Dr. Cox, Scrubs
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06-20-2002, 10:16 PM
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Pupil
Join Date: Mar 2002
Posts: 19
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That sounds like a lame excuse for the poor performance. It sounds like Palm's old line where they said that nobody would want to have color or multimedia on a PDA. In reality it was just a weak defense for their PDAs that didn't provide those features.
Quote:
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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I don't know about anyone else but I can see a noticeable improvement by overclocking my iPaq to 236 MHZ. Everything seems to run a little smoother and the frequency of slow screen redrawing and program pauses is noticeable reduced. I for one was expecting a marked improvement over my existing iPaq because the improvements mentioned above were realized with only a 30 MHZ increase. Shouldn't we expect a noticeable improvement if the clock speed doubles? Likewise I don't think that PocketPC has reached its full potential and Microsoft should not be intentionally plateauing its performance.
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06-20-2002, 10:39 PM
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Intellectual
Join Date: Oct 2003
Posts: 157
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Intel was the exclusive Pocket PC processor manufacturer. The fact they didn't take the rather large V4 ARM codebase into consideration during processor designs and testing shows they are totally clueless. If the Pocket PC 2002 apps, Windows CE.NET apps, Palm V5 apps, and smartphone apps all run more slowly on this thing why would anyone want to buy it at all? Give me the old ARM 206 processor anyday.
Charles
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