Looking at the top, you’ll see that the redesigned 1.4GHz quad-core System on Chip (SoC) with metal shielding is in exactly the same location as the previous SoC on the Pi 3, although the traces running from it have moved around. More on the SoC later…
The next biggest change on the top side is the new wireless circuitry. All of the components have moved from the underside to the topside, and they’re now hidden underneath metal shielding with the added touch of a Raspberry Pi logo embossed into the metal. The small, rectangular chip antenna at the top left on the Pi 3 is gone, and is replaced by the same PCB antenna, licensed from Proant AB, that’s on the Pi Zero W.
Over on the right hand side, the LAN chip has shifted slightly and the four new Power over Ethernet (PoE) pins sit just below the GPIO. These will plug into the forthcoming PoE HAT from the Raspberry Pi Foundation and enable the Pi to get both power and networking over its pins through a single cable.
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