The Raspberry Pi Compute Module 4 was destined to be embedded into a range of carrier boards. Initially, we start with the Compute Module 4 IO board and then design our Compute Module 4-powered product using the various features the IO board provides. For example, Experimental Pi's recent Compute Module 4 powered retrogaming handheld. But the Over:Board project, currently seeking funding via Indiegogo, aims to take the carrier board design a little further, with a Mini-ITX board designed for the Raspberry Pi Compute Module 4 that aims to turn your Compute Module 4 into a PC.
The Over:Board Mini ITX carrier board measures 6.7 x 6.7 inches (170 x 170mm) and features a mixture of Raspberry Pi and PC centric interfaces.
From a Raspberry Pi point of view, we have the new dual header interface used to connect the Compute Module 4 to Over:Board. Nearby we have a HAT-compliant 40-pin GPIO header, so we should be able to use our favorite add-on boards.
Over:Board's typical PC interfaces consist of a 24-pin ATX power interface and a SATA interface with a USB controller that can be used as a boot device. Interestingly, there is a full-size PCI-e slot that enables the use of a PCI-e card. Sadly, the PCI-e interface is limited to 1x, a limitation of the Compute Module 4, but that should be enough for most users.
On the back panel, we have connectors for audio (input and output), a micro SD card slot, two USB 2.0 ports, and Gigabit Ethernet. Video output comes via two full-size HDMI ports. Unusually, an RS232 COM port is present, to be used for serial / UART connections with the Compute Module 4. The final port is micro USB, used for flashing operating systems to the Compute module 4 onboard flash storage (if you are using that particular variant).
Over:Board is currently in the early development phase, so there are no physical units. The goal of crowdfunding is to generate funds to secure prototypes from three different manufacturers. Some of these prototypes are on offer as perks/rewards for supporting the project.
The final production board is set for release in September 2021 for £99 ($135). If you can't wait that long, prototypes are available from March 2021 for £199 ($270) and in May 2021 for £149 ($202). Remember, before pledging your money, crowdfunding is not "buying" a product; rather, you are showing your support to help the creator make the project real. Only pledge your money if you are happy to accept the risk.