The Pi 4 brings USB 3.0, true Gigabit Ethernet, two 4K HDMI outputs — and for the first time a choice of RAM (1, 2 or 4 GB, later 8). The $35 entry price stays, but from now on the Pi is also a serious desktop and server machine. One sore point: the first revision has a USB-C charging flaw that acts up with “smart” cables.