Memory (RAM). Some apps and features won’t work on phones with less than 1 GB of RAM. To see how much memory your phone has, check the manufacturer’s website or your phone’s documentation.
Microsoft did not specify exactly which apps or features won’t work on phones with less than 1GB of RAM. However, looking at the list of all announced Windows Phone 8 devices in our Windows Phone Gallery, we can see that most devices out there will not be affected by this limitation (Nokia decided to put 1GB of RAM for its Lumia 810, 820 and 822 phones despite having a WVGA resolution), with the exception of the HTC 8S. The lower-end HTC 8S is currently the only announced Windows Phone 8 device that features only 512 MB of RAM, which means that it may have some software limitations similar to the 256MB devices in the Windows Phone 7.x era.
We do expect there will be more lower-end Windows Phone 8 devices that features only 512 MB of RAM however, such as the rumored Nokia Zeal, Nokia Flame, as well as the Huawei Ascend W1. Perhaps we might find out more about what these limitations are when the final Windows Phone 8 SDK gets released during BUILD 2012 tomorrow.