Microsoft is putting an end to free style design and is specifying three variants of Windows Phone 7 devices, that prescribe form factor, CPU, graphics and possibly more. Each variant, or “chassis”, specifies one of the most popular form factors, though we only have specifics for Chassis 1 for now.
Chassis 1 describes the requirements for “big touchscreen” phones. There’s no minimum screen size or resolution yet, but previous rumors suggested 3.6” WVGA. The minimum requirements for the CPU are 1GHz (that’s right - minimum) and hardware graphics acceleration is mandatory. Obviously Microsoft is really keen on ensuring smooth and comparable UI experience over various devices.
There are less details about Chassis 2 and Chassis 3. Chassis 2 will have slide-out QWERTY keyboards in addition to the touchscreen (we guess CPU and graphics requirements are the same) and the Chassis 2 devices are said to be Treo-like (strange, because the Treos are bars with portrait QWERTYs, there’s no sliding).
It’s the Windows Phone 7 Chassis 3 devices that have the bar form factor. That would make them Treo-like, rather than the Chassis 2 phones, which sound more like, say, the Sony Ericsson XPERIA X2.
Previous rumors about the minimum hardware requirements for Windows Phone 7 devices also listed minimum camera resolution, GPS, Wi-Fi and even a minimum set of hardware buttons. These vary quite a lot, so we’re not sure about the specifics, but it looks like Windows Phone 7 devices will be inhabiting the high-end segment only and Microsoft will have a firm grip on the used hardware via stringent licensing procedures.
The first Windows Phone 7 Chassis 1 devices should launch in time for this year's holiday season. There's no word on when Chassis 2 and 3 phones will launch.