While earlier Pi Compute Modules used a SO-DIMM form factor, the CM4 uses a pair of 100-pin mezzanine connectors. Raspberry Pi 4 Compute Module. Not shown: two mezzanine connectors on the underside.

Various carrier boards are already on the market for the CM4, but the standard CM4IO Board is typical (Fig. 4). It exposes all of the interfaces via connectors and even includes a Raspberry Pi HAT ...

The board measures 146 x 80mm (5.7″ x 3.1″) and features a connector for a Raspberry Pi CM4, as well as full-sized ports and a GPIO header that allows the board to work with standard Raspberry ...

For more information on full specifications on the Piunora Raspberry Pi CM4 open-source carrier board jump over to the official Crowd Supply website by following the link below.