Originally Posted By: Vikas
What in the name of the God, iPhone asks for 4GB free space before allowing an upgrade? Does anybody know how long it will take to download 4GB to start the upgrade?
The download itself is anywhere between 800mb and 1.2gb, depending on the device and feature set.
It needs the extra memory for unpacking and installation, and also to maintain a working ios7 until a working installation of 8 is confirmed. At one point, the device memory has to support BOTH operating systems.
If tight for space, a lot of 16gb device users are installing though iTunes/computer interface, which supposedly offloads some of the memory requirements to the host computer.
We've installed 8 on a couple A5/16gb pads and a phone, all without issue. They all run 8 just fine. On the slowest device, the whole process takes about 30-40 minutes, tops.