Microsoft is finally making it clear that swapping or adding a Micro-SD card to a Windows Phone 7 device like the Samsung Focus ,which has user accessible slot, isn’t recommended at all. There has bit a lot of controversy around this subject ever since the company claimed that WP7 wouldn’t support user expandable memory back in March during the MIX conference. Microsoft has posted a lengthy post on their support site explaining that if a Windows Phone 7 is build with a micro-sd slot it doesn’t mean that the user can or should change the memory card that shipped with the handset. The memory card slot is intended to be used only by the OEMs. As a matter of fact several Samsung Focus users who decided to change the memory card on their devices are now facing performance problems and AT&T, who claimed that they would allow users to change the memory configuration of their WP7 devices, decided to change its tune and deal directly with Microsoft on this matter.This basically all boils down to the type and quality of the Micro-SD card as stated below:
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.RemarqueIn 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 Phone7 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.
I guess that if you plan on doing it anyway, your best bet would be to buy a super high rated Micro-SD and not be a cheap bastard…