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Carrier board extends Raspberry Pi Compute Module 4 with PCIe, SATA

Jan 6, 2021 — by Eric Brown 10,701 views

On Indiegogo: a $134 “Over:Board” Mini-ITX carrier for the Raspberry Pi CM4 with a full-sized PCIe slot, GbE, COM, 2x HDMI, a USB 2.0 hub, USB-based SATA and audio, an RTC, and a 24V ATX input.

In October, we covered a Turin Pi 2 Mini-ITX carrier board that can cluster up to four Raspberry Pi Compute Module 4 boards. Now on Indiegogo you can find a Mini-ITX board designed to extend a single RPi CM4 with features including dual HDMI, SATA, and full-size PCIe. The carrier fits inside standard Mini-ITX, Micro-ATX, and ATX cases.

Over:Board renders
(click images to enlarge)

The Over:Board is the debut product launch from a UK-based engineer named Ross Nicholls who has spent 20 year in the computer industry and has worked on about 35 PCB projects. The flexible funding Indiegogo campaign offers the motherboard for 99 UK Pounds ($134) if you are willing to wait until September for the final production product. A pre-production version due in May costs 149 Pounds ($202) and an earlier prototype due in March costs 199 Pounds ($270).

Project backers need to bring their own, Linux-powered, $25 to $90 Raspberry Pi Compute Module 4, which has the same Broadcom BCM2711 SoC with 4x 1.5GHz Cortex-A72 cores used by the Raspberry Pi 4. The module ships with 2GB to 8GB LPDDR4-3200 RAM and 0GB to 32GB eMMC.


The CM4 provides a GbE controller with PoE support, optional 802.11ac with BT 5.0. There is also new support for dual 4K HDMI ports and PCIe 2.0 — both features that are exploited by the Over:Board. The CM4 uses the sole USB 3.0 interface for PCIe instead of for the USB host hub, as does the RPi 4.

The Raspberry Pi CM4 switches from the SODIMM connector of the RPi CM3+ and CM3 to dual (low speed and high speed) 100-pin connectors. This enables a smaller 55 x 40 x 4.7mm footprint compared to the earlier 67.6 x 31mm but prohibits backward compatibility to earlier carriers.

The Over:Board features a PCI-Express 1x v2.0 slot with space for full-size cards. The carrier provides dual USB 2.0 host ports from a 4-port hub plus a micro-USB client port. There is also a USB-based SATA controller and a USB connected audio IC driving 3.5mm line-out and mic-in jacks.

Over:Board detail views
(click images to enlarge)

The Over:Board is further equipped with GbE, RS232 (DB9) COM, and 2x HDMI ports. You also get a microSD slot, as well as front-panel, fan, and UART headers.

The carrier board runs off a 24-pin ATX power header and provides a 4-pin alternate power input. A Real-Time Clock with backup battery is also available.

Further information

The Over:Board is available for the next 30 days on Indiegogo starting at 99 UK Pounds ($134) for September delivery, and more for prototypes that ship earlier. More information may be found on the Over:Board Indiegogo page.

(advertise here)

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