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  #1  
Old 07-15-2005, 11:00 AM
Jon Westfall
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Default An Interesting Power Point On Persistant Storage

<div class='os_post_top_link'><a href='http://blogs.msdn.com/windowsmobile/archive/2005/07/14/438991.aspx' target='_blank'>http://blogs.msdn.com/windowsmobile.../14/438991.aspx</a><br /><br /></div><i>"Remember that RAM requires power to keep its data. The amount of power needed is linear with the amount of RAM. That is to say, 64M of RAM needs twice as much power to keep it running as 32M does. 128M needs four times as much power as 32, etc. And this power drain is constant. The RAM is sucking your batteries dry while the device is in use and while it's suspended. It even continues to drain your batteries when they are "critically low" and the system won't let you turn it on. Also, people didn't buy 128M RAM devices for the program space. They bought them to store stuff in. And those devices had lousy battery lives as a result."</i><br /><br />Robert Levy dropped us a note with this post from Mike Calligaro in the Windows Mobile Team Blog. Persistant storage has always sounded nice to me, but after reading this post, it hammers home the point that it really will change the way we use our devices. I never appreciated how much my battery was monopolized by RAM (If I had really thought about it, I probably would have realized this, but like I said, this post hammered home the point to me in a way I hadn't really thought to think of ). For all of you who are still skeptical about Persistant Storage in WM 2005, take a read through. And if you think you know why all the hype is warrented and welcome PS, take a read as well - it may make you think more than you had!
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  #2  
Old 07-15-2005, 11:42 AM
Menneisyys
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Interestingly, the guy doesn't say anything on the write optimizations/caching at all.
 
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  #3  
Old 07-15-2005, 12:25 PM
shk718
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i just bought the samsung i730. the battery life sucks!!!! but it looks like it was designed for WM5 - so the question of the day is how do we force Verizon to give us an upgrade??
 
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Old 07-15-2005, 01:15 PM
Dalantech
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I was wondering if batter life would improve since you don't have to "feed" RAM when the device is turned off. I'm starting to see why Dell opted for a 1100 MaH battery in the Axim x50v -they probably designed it for WM 5...
 
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  #5  
Old 07-15-2005, 01:51 PM
surur
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A a 128Mb ram device owner, currently using 46Mb for execution without any web pages open, I think 64Mb ram will continue to be limiting. When I upgrade my Loox 720 to WM5, I will benefit in two ways.

1) The artificial low battery restriction will have been removed, allowing me to get full benefit from my 1640mAh battery.
2) I will still have persistent storage.
3) I will be immune from future growth of software size, as I will always have more ram than most, meaning I can do much more at the same time.

The downside is that I use 10% of my battery capacity per day to keep my 128Mb ram alive, but my OEM provided a large 1640 battery to take account of this. I will continue looking for 128Mb ram in any device I buy, because I want more than I need in day to day use, not just enough.

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Old 07-15-2005, 01:55 PM
jngold_me
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Am I correct in understanding that WM5 will still allow a "suspend" mode for keeping state, similiar to what we have today?

Menneisyys,

Are these optimizations you speak of in the realm of the OS and are transparent to application developers, or will app developers need to adhere to certain programming methods to work "well" in the WM5 platform?

TIA!

Surur,

At this present moment I have a VB database app open, World Offline, and the full home page for CNN loaded in memory (in addition to various Today screen plugins) and I have 22.46mb in use. The only thing I can think of as to why your are using so much memory is VGA vs QVGA. I still find it hard to believe that such a disparity in memory usuage exists between the two (although stranger things do occur).
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  #7  
Old 07-15-2005, 02:02 PM
Menneisyys
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Quote:
Originally Posted by jngold_me
Menneisyys,

Are these optimizations you speak of in the realm of the OS and are transparent to application developers, or will app developers need to adhere to certain programming methods to work "well" in the WM5 platform?
Dunno. There're only few apps (PIE, Netfront, SimpleSMS etc.) that do mass writing to the cache directory/database file. Therefore, most 3rd-party apps will work OK in WM5, at least speed-wise, without touching them.

I don't know whether the developers of WM5 have gone for the less resource-friendly, but certainly more compatible 'transparent ' mode, or, do they enforce the programmer to do some work instead (for example, instead of creating one file for each Web page resource (GIF's, JPG's, JavaScript files, CSS files and the main HTML page) - file creation speed sucks even more in the File Store than file writing speed - , concatenate their contents to just one file.) Both are possible.
 
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  #8  
Old 07-15-2005, 02:06 PM
Phillip Dyson
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Why is it none of the "official" will answer questions about the lifecycle of ROM memory once everything starts to be written to it?
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Old 07-15-2005, 02:14 PM
Menneisyys
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Quote:
Originally Posted by sojourner753
Why is it none of the "official" will answer questions about the lifecycle of ROM memory once everything starts to be written to it?
Well, this question has been partly answered by HP's not providing the WM5 upgrade for the iPAQ rx3xxx (the worst PDA, file store life expectancy-wise) :devilboy:

I'm also afraid of the upgrade because of this fact. I'll try to find ways of relocating the Registry and the WinCE databases (especially if there will be a lot of PC -> PDA, for example, mail synchronization) back to the main memory, I think... My PIE/Netfront cache will also go back to the main memory. I don't want to have a paperweight (my PL720's warranty will run off this Autumn...)
 
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  #10  
Old 07-15-2005, 02:21 PM
CESkins
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Quote:
Downsides? Yes, nothing is free. Flash is much slower than RAM. Reading and writing large amounts of data will take longer on a PS device than it did on a RAM device. That initial sync that pulls down 400 contacts and 5000 emails will take longer. Some write operations will seem a bit more sluggish
The above quote is the reason why despite the gains in battery life, the new move towards persistant storage in the form of FLASH ROM does not excite me. I use Textmaker, PlanMaker, and ListPro (with several ~ 1 MB databases). Textmaker &amp; PlanMaker take a relatively long time to load/run when stored in FLASH ROM (or even an SD card) than RAM. ListPro also takes longer to open, search, and store large databases when they are stored in ROM. Since I use these apps frequently (especially ListPro) these delays can add up to a significant amount of time lost during the day. If newer devices come with faster FLASH ROM than currently in use or utilize a very good caching algorithm that may offset some of this slowdown.

Personally the reason I moved to a 128 MB RAM PDA (Loox 720) was for speed. Battery life was a moot point because I could charge my PDA anywhere (including the car while I drove using a retractable cable and multipurpose pocket adapter). Loosing my RAM contents was also rendered less of a nuisance/catastrophe by using automated backup software and storing mission critical data files on an SD/CF or File Store. My guess is that those of us who still want maximal speed when using their PDA will simply choose to leave certain apps like Textmaker running all the time rather than closing them to avoid slow reloads. Also to prevent having to reload the app, the PDA will never fully be turned off (thereby effectively closing running apps) during the working day. Since the RAM will always be in use, this renders the battery life savings gained by full power off moot (at least for me). The other advantages to persistant memory storage outlined in the article however will still hold true. From my standpoint, WM5 memory model appears to be a mixed bag.

Quote:
Why is it none of the "official" will answer questions about the lifecycle of ROM memory once everything starts to be written to it?
It's finite (probably like SD and CF on the order of a few thousand writes). This will be one of the reasons to upgrade a relatively old device to a newer model. . My biggest fear is "loss" of the persistant storage. Some individuals reported their File Store simply disappeared and the system could not read from/write to it. The solution in some cases was to get a new PDA. If we start storing everything in one big file store, what's to say we won't end up loosing everything.
 
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