Leaked Windows Phone 7 docs describe updates, customization

Additional details on the underlying architecture of Windows Phone 7 have leaked, thanks to a document obtained by the Dutch website tweakers.net. The document is from February 2010 and is marked as Revision 3.0. Beneath the Microsoft Confidential watermark there is a disclaimer: “The Architecture for Windows Phone OS 7.0 describers features that are subject to change, and should therefore be considered preliminary.” Microsoft has already disclosed a few of the hardware requirements for its upcoming mobile OS, but the document does give a few more tidbits.

Requirements

Many broad strokes of the hardware requirements have already been disclosed officially. Microsoft says the requirements that all Windows Phone 7 smartphones must meet are based on market research and feedback from vendors. Intel may want to conquer the smartphone market with Moorestown, but Windows Phone 7 makes high-performance ARM processors compulsory, so Intel’s not invited. Instead, the Qualcomm Snapdragon family and Texas Instruments OMAP meet Microsoft’s demands. Windows Phones must have back, home, and search buttons, two volume buttons, a power off button and a camera button. A multitouch touchscreen is also required. Surprisingly, Bluetooth 2.1 + EDR is the latest version mentioned (versions 3.0 and 4.0 are missing), though this might only be indicative of the minimum requirement.

For high-end Windows Phone 7 devices, the requirements are a bit more comprehensive as described by the Performance Chassis. In addition to complying with all the requirements of the Basic Chassis, the standard resolution is 800×480 (as opposed to 480×320). The Performance Chassis also specifies a gesture interface, though how it is different from the standard interface is not yet known. The document also notes the Performance Chassis will have more demands, such as in the area of memory, but these have not yet been defined.

A Windows Live ID is required to use Windows Phone 7 (similar to how iTunes is required for iPhone OS and how Gmail is linked to Android). It will be needed for synchronizing data such as contacts and text messages with Microsoft’s servers and to access the Marketplace (the only way to get apps). After the device is first turned on, and the user has chosen the language and agreed to the terms and conditions, he or she will be asked to enter their Windows Live ID, or register for a new one. For Windows Live ID services to function correctly, the device must have a Genuine Windows Phone certificate, which comes with the phone and ensures that it is identified as running Windows Phone 7.

Customization

Updates are distributed through Microsoft Update, meaning users will no longer have to wait for providers and manufacturers to ship a new ROM like they did with previous versions of Windows Mobile (or more commonly, didn’t; most providers and manufacturers barely bothered). Providers will also be able to push their own customizations via Microsoft Update. The feature is called Phone Update and operates via two channels: over-the-air (OTA) and USB. Minor updates will be delivered OTA, with major updates installed via USB tethering, using the Zune software installed on a PC.

Providers and manufacturers will not be able to customize Windows Phone 7 as much as previous versions of Windows Mobile. Nevertheless, they’ll be able to change the default search provider in Internet Explorer Mobile from Bing to any company they have a search deal with. For other applications, however, Bing will remain the default. Vendors will also be able to add to the Favorites list in IE. They can change the boot screen, as well as add their own wallpapers and ringtones. Also, the camera software settings can be tweaked.

Only minor changes can be made to the interface: connection icons in the notification area such as for 3G and WiFi. Providers and manufacturers can also add their logo and tiles to the homescreen (standard Microsoft tiles cannot be removed). They can also add their own applications directly to the ROM of a device, but these are bound by strict rules and must be approved by Microsoft in advance. A maximum of six applications can be added, which can only occupy a maximum of 60MB.

Structure

Windows Phone 7 is built on top of Windows Embedded CE 6.0, and so a lot of the low-level aspects of its design are already documented. Relative to the Windows CE 5 kernel used in Windows Mobile 6.x, Windows CE 6 is a lot more similar in design to a regular desktop OS. Given enough memory, Windows CE 6 can run up to 32,000 or so processes, in contrast to the 32 supported in its predecessor (31, in fact, as the 32nd process is the kernel itself).

The memory management of the new OS is substantially different. The 32-bit memory space is split into two, a 2GB upper part dedicated to the kernel, and a 2GB lower part dedicated to non-kernel code. This lower part is then split into two 1GB parts. The upper 1GB part is used for various shared structures like system libraries; the lower 1GB part is for use by programs for whatever they need. Each process gets its own copy of the lower 2GB part, so each process can allocate up to 1GB of memory.

This gives programs a lot more breathing room than in Windows Mobile 6. That OS still had the 2GB/2GB split between kernel and nonkernel memory, but the nonkernel memory was organized very differently. The result was that each process had only 32MB of memory to call its own, along with a shared block of memory a little under 1GB in size shared between all processes.

These make Windows Phone 7 a lot less constrained than Windows Mobile 6, which in turn makes it a much better application platform. Perversely, it also means that Windows Phone 7 is better-suited to multitasking than its predecessor.

The kernel and nonkernel parts contain what one would more or less expect; the kernel part contains the kernel itself, the file system, graphics rendering, and the update system. The nonkernel, user space part, contains the Windows Phone 7 shell and any applications.

Windows Phone 7 uses two file systems: IMGFS and TexFAT. The former was designed for storing updateable system images. The latter is a transactional version of the exFAT filesystem; exFAT improves on the venerable FAT filesystem by allowing files larger than 4 GB. TexFAT is used for user storage.

The user files are organized via a Unified Storage System which provides pplications and users with a unified view of files regardless of their location (internal memory or memory card) or filesystem. This also potentially means that not all the files from the memory card may be removed; if a memory card containing key files is removed or wiped, the phone will only be able to make emergency calls.