Devices using Windows Phone 7 will have just three main form factors to choose from, the company said during the most recent episode of the Frankly Speaking podcast. The hosts, who are both Developer Evangelists for Microsoft Australia, confirmed details of the chassis program that had been rumored for much of last year. Chassis 1 is now known to be limited to full-touchscreen phones that use a 1GHz processor or faster and will be the first to meet the late 2010 shipping target.
Chassis 2 phones will resemble many common Windows Mobile phones and combine a touchscreen with a sliding QWERTY keyboard. Chassis 3 isn't explained but is likely to involve phones with fixed-in-place keyboards. Other chassis details weren't discussed, though Microsoft has already said that Chassis 1 hardware will need a wide VGA (800x480) or better display. 3G, GPS and Wi-Fi are also believed to be requirements.
The policies are a stark contrast against Microsoft's attitude towards Windows Mobile, where it has often touted choice of design as a positive. Windows Phone 7 is intended to provide much tighter integration between hardware and software and will have Microsoft writing and supplying many of the drivers itself, which should speed up development and permit fast firmware updates but also limit the variety of hardware. Vendors like Apple and Palm have lately been given favorable reviews precisely because their mobile OS interfaces and features are often tailored to a narrow range of hardware.
Alongside the chassis details, it's also rumored that many of the Xbox-style games built using XNA may not be possible until Windows Phone 7.1, which is unlikely to show until 2011. The source behind the slip didn't explain why, although it's implied the developer framework for outside apps isn't ready.