The Raspberry Pi CM4IO board has been designed for use with the Raspberry Pi Compute Module 4 to allow for additional interfaces to be used within your design. The CM4IO board contains many of the interfaces that the Raspberry Pi 4B has, the main difference is the addition of a PCIe x1 socket.

External power connector (+12V, +5V)
2 x full-size HDMI 2.0 connectors
2 x USB 2.0 connectors, with header for two additional connectors
Gigabit Ethernet RJ45 with PoE support
Micro USB socket for updating Compute Module 4
MicroSD card socket for Compute Module 4 Lite (without eMMC) variants
PCIe Gen 2 x1 socket
Standard fan connector
2 x MIPI DSI display FPC connectors (22-pin 0.5 mm pitch cable)
2 x MIPI CSI-2 camera FPC connectors (22-pin 0.5 mm pitch cable)
Standard Raspberry Pi HAT connectors
Real-time clock with a battery socket and ability to wake Compute Module 4
Various jumpers to disable specific features, e.g. wireless connectivity, EEPROM writing