Windows Phone 7 Secure Digital Card Limitations

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Article ID: 2450831 - View products that this article applies to.
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Summary

This article provides information to help you understand how Windows Phone 7 devices use SD cards, the performance requirements of SD cards for Windows Phone 7 devices, and how your phone will behave if you remove the SD card or add a new one.

Some Windows Phone 7 devices include a Secure Digital (SD) card slot underneath the battery cover. If you buy a Windows Phone 7 device that includes an SD card slot, you should be aware of several important differences from other devices that use SD cards:

  • The SD card slot in your phone is intended to be used only by the Original Equipment Manufacturer (OEM) that built your phone and your Mobile Operator (MO). These partners can add an SD card to this slot to expand the amount of storage on your phone.
  • To help ensure a great user experience, Microsoft has performed exhaustive testing to determine which SD cards perform well with Windows Phone 7 devices. Microsoft has worked closely with OEMs and MOs to ensure that they only add these cards to Windows Phone 7 devices.
  • You should not remove the SD card in your phone or add a new one because your Windows Phone 7 device might not work properly. Existing data on the phone will be lost, and the SD card in your phone can't be used in other Windows Phones, PCs, or other devices.

More information

Understanding How Windows Phone 7 Devices Use SD Cards

If your Windows Phone 7 device contains an SD card, you should think of it as a permanent component of your phone, not as removable storage. The Windows Phone 7 operating system treats the SD card as an integrated part of the phone. This is in contrast to other devices, where you can use an SD card to increase the memory available to the device at any time or to transfer files to other devices. The phone’s operating system integrates the SD card with the phone:
  • When you start your phone for the first time.
  • When your phone is reset to its original factory settings. This is called a factory reset. This is a task that is typically only performed by OEMs or MOs.

When the operating system integrates the SD card with your phone:
  1. It reformats the SD card.
  2. It creates a single file system that spans the internal storage and the SD card.
  3. It locks the card to the phone with an automatically generated key.
From this point on, the phone’s operating system uses all of the available memory as a single storage space for storing applications and data. The phone will stop working properly if you remove the SD card, and the SD card cannot be read by another phone, device, or PC.


Performance Requirements for SD Cards

The SD card in a Windows Phone 7 device must meet certain performance requirements for the phone to function optimally. If the SD card does not meet these performance requirements, the phone will have portions of memory that meet the performance needs of the operating system (the internal storage) and portions of memory that do not meet the needs of the operating system (the SD card). This can lead to poor and unpredictable performance when using the phone. This article uses the term Windows Phone 7 compliant to refer to SD cards that meet the performance requirements for Windows Phone 7 devices.

Determining whether an SD card is Windows Phone 7 compliant is not a simple matter of judging its speed class. Several other factors, such as the number of random read/write operations per second, play a role in determining how well an SD card performs with Windows Phone 7 devices.


What to Expect if You Modify the SD Card Slot in a Windows Phone 7 Device

You may experience the following issues if you remove or replace the SD card in a Windows Phone 7 device, or if you add an SD card to a Windows Phone 7 device that has an empty SD card slot.
  • Removing the SD Card: If you remove an SD card that has already been integrated with the phone, the phone displays an error message that tells you to reinsert the SD card. All phone functionality is disabled except for the ability to make emergency calls. The phone will function normally again only if you reinsert the original SD card and then start the phone.
  • Integrating a Phone with a non–Windows Phone 7 Compliant SD Card: If a non–Windows Phone 7 compliant card is integrated with the phone, you might notice the following performance issues when you use your phone:
    • Applications might start more slowly or not at all.
    • Transitions between some application screens might stutter.
    • Some applications might not respond at times.
    Note In some cases, these performance issues might only be evident after using the phone for some time. For example, if your phone has 8 GB of internal memory and you integrate a non-compliant SD card with the phone, you might notice the performance issues only after the 8 GB of internal memory is filled with applications and media.
  • Integrating a Phone with a Different Windows Phone 7 Compliant SD Card: If your phone already has an SD card and then a different Windows Phone 7 compliant card is integrated with the phone, you will lose any data that was stored on the phone, including any applications that you installed from the Marketplace hub. Examples of data that might be stored on the SD card include manually linked contacts, start customizations, and data that applications do not store remotely.
  • Adding an SD Card to a Phone with an Empty SD Card Slot: If you purchase a Windows Phone 7 device with an empty SD card slot and you add an SD card to the phone after you start it for the first time, the phone will continue to work properly, but it will not recognize the SD card. The phone will not save applications or files to the SD card.

    To use an SD card with the phone, a Windows Phone 7 compliant card must be integrated with the phone in one of the scenarios described above in the section Understanding How Windows Phone 7 Devices Use SD Cards.

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Article ID: 2450831 - Last Review: July 16, 2013 - Revision: 8.1
Applies to
  • Windows Phone 7 Consumer
Keywords: 
kbwp7 KB2450831

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