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DISASSEMBLED: Windows Phone 7, Memory Management and microSD Cards
Posted by Arne Hess - on Thursday, 28.10.10 - 13:17:34 CET under 02 - Windows Mobile News - Viewed 39082x
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One of the limitations of Windows Phone 7 is, that Microsoft's new mobile OS isn't supporting user removable flash memory like microSD cards, as supported by Windows Mobile, but Windows Phone 7 uses embedded memory like Apple's iPhone does. However, this isn't a big deal as long as the Windows Phone 7 device in use has enough memory. As of today the ODM's memory size of choice seems to be between 8 and 16 GB (most of the recently announced Windows Phone 7 smartphones will have 16 GB anyway). However, even if Windows Phone 7 isn't featuring a customer swappable flash memory, it seems that some handset manufactures are using micro SD cards anyway.

While the microSD card is hidden on most Windows Phone 7 devices, it's not user accessible but it definitely makes sense for handset manufactures to use microSD instead of embedded flash memory. Flash memory can be pretty expensive and limited in stock while microSD is a bread and butter technology largely available today. And it has another benefit for the handset manufactures: They can easily upgrade the memory even within the device lifecycle or offering different customizations for different carriers and markets; for instance the HTC HD7 in Europe featuring 16 GB while the North American version features 8 GB only!

On the other hand, the Windows Phone 7 OS addresses the RAM memory and the internal memory as a kind of JBOD drive (Just a Box Of Disks/Just a Bunch Of Drives) where multiple physical memories (or drives) are combined into a single virtual disk. However, addressing memory this way doesn't provide any data redundancy (as known from RAID systems). As the name implies, disks are merely concatenated together, end to beginning, so they appear to be a single large disk and that's indeed the way Windows Phone 7 handles the memory. The flash memory of Windows Phone 7 isn't designed to be user swappable - all the flash memory is seen as one single drive and removing one part of the memory breaks down the whole device.

However, it seems that the microSD cards can be changed anyway, especially because the OS itself is part of the not removable ROM and therefore available even after a memory exchange. For the test, I've opened a brand new HTC HD7 (preproduction device) and replaced the preinstalled SanDisk 8 GB (Class 2) microSD card with a Samsung 8 GB (Class 6) microSD card.

On Windows Phone 7, this memory replacement requires a factory restore (hard reset) to initialize the new microSD card but even after several factory resets, it looked like it's impossible to change the microSD card and get the HD7 working again because the device always booted with the following error message:

However, after carefully putting the new microSD card into the microSD card holder again, the HTC HD7 finally booted and started with the Windows Phone 7 device configuration screen:

I haven't experienced any differences in speed or stability so it definitely seems that the new microSD card was fully accepted by the device (after the initial trouble). On the other hand I have to admit that I replaced a 8 GB card with a 8 GB card (even if both support different classes) and therefore it's yet not a proof that the HD7 will also handle 16 GB cards (which it should because some carrier configurations feature 16 GB) or even 32 GB microSD cards. Nevertheless, it definitely seems that a memory upgrade/change is doable and users might be able to easily upgrade the memory of Windows Phone 7 smartphones - as long as they know where the microSD card is placed.
However, at this point it's not confirmed that all of today's Windows Phone 7 devices will be indeed featuring microSD memory but it's yet just an assumption that most - if not all - will indeed use microSD. Furthermore it's not confirmed that all devices with microSD cards will accept the swap of the original memory card but there's a good chance that this is widely supported! Nevertheless, this topic definitely needs further investigations!

UPDATE: HTC just informed us that the commercial HTC HD7 isn't shipping with Class 2 microSD cards but something (not named) better. That's definitely good news but even it's even more interesting to know that (some?) Windows Phone 7 smartphones can also work with slow Class 2 microSD cards.

Cheers ~ Arne


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Posted by Craig on 28.10.10 - 14:14:15

Could you post details of how you gained the ability to remove the card. I'm keen to put a 32 gb card in instead of the original 16 gb but want to dissasseble as litlle as possible. Any help would be appreciated.

Posted by davide on 28.10.10 - 15:33:23

Great work! I know its unlikely but can the same be done with the Omnia 7 UK version? it onlyhas 8gb and it would be nice to think that i could add memory to it.

Posted by Montecristoff on 28.10.10 - 15:48:41

@Craig : dereckcranson done this operation two days ago
I just quote him here :

If you take off the cover to access the battery you can see 8 of the 10 screws that have to be removed. The other 2 are under the smaller back cover. The sd card is in a normal sd card slot with a bit of tape over the end. take the card out like you would a card from any other phone (i.e. push down and it pops up). one of the screws has a void sticker on it.

from xda dev post #46 and following...


Posted by Arne Hess on 28.10.10 - 15:50:39

@Graig: It's not too hard to get the cover off from the main body but for warranty reasons I don't want to go into any further details. However, I can tell you you better have a small screwdriver by your hand to get the cover removed and the microSD card lifted. Without a screwdriver you won't be able to get the card out of the holder.

@davide: Well, I'm somewhat sure that the Samsung Omnia 7 is also featuring a microSD card only and therefore I don't think it's unlikely. However, here it seems to be a little bit more complicated since it seems to involve the screws to disassemble the device.

@Montecristoff: I haven't removed a single screw to get the cover off. But yes, there might be different ways!

Posted by Riker on 28.10.10 - 18:17:16

Arne: Did you have to break any warranty seal?

Posted by Arne Hess on 28.10.10 - 22:40:24

@Riker: No, I hadn't but then again, it was a kind of preproduction device (even if I think the hardware was pretty final) where it might worked better or different to commercially available devices.

Posted by JoKa on 29.10.10 - 05:03:45

The stock SD card is a SanDisk Class 2? But MSFT says that the SD cards in WP7 phones use a special, high capacity card. They're lying to us.

Posted by Riker on 29.10.10 - 10:38:05

Thanks Arne!

Posted by Arne Hess on 29.10.10 - 14:02:05

@JoKa: The microSD of my pre-production unit was Class 2 but in the meantime HTC has confirmed us that the commercial HD7 isn't sporting Class 2 microSD cards.

Posted by docchris on 29.10.10 - 15:43:37

i got my back off just by pulling - its held on by VERY firm grips/clips around the edges, it then snaps back on

some guys on XDA say once it reformats it works with 32gb cards - my 32gb one should be here tomorrow so i will let you know!

Posted by docchris on 30.10.10 - 13:52:01

the 32gb card works perfectly and show 29.99gb available space

Posted by Arne Hess on 30.10.10 - 17:21:00

@docchris: Ah, lovely! :-D Thanks a lot for the update! With my hunt for a 32 GB I was unsuccessful and now awaiting the Amazon delivery.

Posted by docchris on 01.11.10 - 13:54:19

well an update on this - while the 32gb card did work perfectly at first, it turns out the card which i bought (from a business too!) was actually a counterfeit one!

when i put the serial number into the kingston website - it said it wanst valid

the writing began to rub off

after a few hours the card died altogether

i contacted the business and they were very very apologetic and said they have been inundated with complaints after they bought a batch of fake cards in good faith.

they did at least give me a full and immediate refund so i have now had to re-order a different 32gb card from a different vendor!

Posted by bazza on 03.11.10 - 11:38:53

How do you remove the back? Its very tightly fitted and i dont want to break it.

Posted by docchris on 03.11.10 - 14:18:02

really it is just grab it in the center and pull (or at least thats how i did it)

it is VERY tight (after you do it a few times its not so tight.

i squeezed my nails under the metal band with HD7 written on it and pulled up and away from the phone and eventually the two grips at the "top" of the lower panel on the left and right hand sides gave way, then i gently pulled it out all the way around

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