VideoCardz came across a photo of the Polaris 10 PCB. It appears both the Radeon RX 480 and Radeon RX 470 will share the same PCB.
It has eight single-sided memory modules with up to 8GB of capacity. The circuit is powered through single 6-pin connector, and the power is split into 6+1 phases, which is actually more than GTX 1080 (5+1).
The reference board comes with four display outputs (three DisplayPort 1.3/1.4HDR and one HDMI 2.0).