NOVA 3 has only been cleared for the 1 GB of RAM tier of Windows Phones, so that means 8/92x series phones.
It technically can be optimized or something for 512 MB devices, but I don't know about the possibility of it happening.
What's up with that actually, my iPod touch 4 ran NOVA 3 rather decently and it's equipped with 256 MB of RAM. what gives?