As with every major Windows Phone revision, Microsoft updates the set of hardware requirements that OEMs must follow when making a device to run their OS. With Windows Phone 8, these requirements have changed slightly from Windows Phone 7.5 "Tango", and somewhat paint a picture of why WP8 won't run on legacy Windows Phone 7 devices.
- Qualcomm Snapdragon S4 dual-core processor
- Minimum 512MB RAM for WVGA phones; minimum 1GB RAM for 720p / WXGA
- Minimum 4GB flash memory
- GPS and A-GNSS; GLONASS is supported if OEMs decide to include it
- Support for micro-USB 2.0
- 3.5mm stereo headphone jack with three-button detection support
- Rear-facing AF camera with LED or Xenon flash, optional front-facing camera (both need to be VGA or better) and dedicated camera button
- Accelerometer, proximity and ambient light sensors, as well as vibration motor (magnetometer and gyroscope are optional)
- 802.11b/g and Bluetooth (802.11n is optional)
- DirectX graphics hardware support with hardware acceleration for Direct3D using programmable GPU
- Multi-touch capacitive touch screen with minimum of four simultaneous points
For one, the minimum RAM requirement has gone up from 256 MB to 512 MB, and if a smartphone maker opts for a high-resolution display they'll have to include 1 GB of RAM at a minimum. Microsoft also makes note that some features of Windows Phone 8 won't run on less than 1 GB of RAM - something that will affect the HTC Windows Phone 8S with 512 MB of RAM - but the affected features haven't been specified.
Also noteworthy is that all Windows Phone 8 devices must include at least a dual-core processor from Qualcomm's Snapdragon S4 range. This is almost certainly to help keep a minimum smoothness standard across the operating system, as with adding more features comes a requirement for more power. Windows Phone is known for being buttery smooth, and Microsoft will certainly want to keep this up.
The remainder of the requirements are things you would expect from a smartphone anyway, such as a rear camera of at least VGA quality with a flash, and a 3.5mm headphone jack. The good news is that the improved hardware requirements mean developers know exactly what they are dealing with while making Windows Phone 8 applications, at the bare minimum at least.