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Here come the Raspberry Pi Compute Module pseudo-clones

Nov 8, 2021 — by Eric Brown 866 views

[Updated: Nov. 11] — Pine64 launched an RPi CM4-like “SOQuartz” module for $35 (2GB) to $75 (8GB) with WiFi/BT and SATA support. Meanwhile, Radxa revealed a similarly RK3566-equipped “Radxa CM3” that also adds USB 3.0. Both modules can use CM4 carriers.

In June, when Pine64 launched its Quartz64 model-A SBC, the company revealed preliminary details for a SOQuartz compute module, which similarly runs Linux or Android on the quad-core, Cortex-A55 Rockchip RK3566. Aimed initially at developers, the SOQuartz has now launched in 2GB LPDDR4 ($40), 4GB ($50), and 8GB ($75) variants, which are priced the same as equivalent RPI CM4 modules. The module has dual 100-pin B2B connectors like the Raspberry Pi Compute Module 4, enabling users to plug into a CM4 carrier board, much like Antmicro’s upcoming, RISC-V based (StarFive 71×0) ARVSOM module.

The launch came a day after Radxa posted specs for an unpriced Rock3 Compute Module, which is confusingly nicknamed the Radxa CM3. The “3” in this case refers to the $35-and-up Rock 3 Model A and the upcoming, more feature-rich Rock 3 Model B SBCs. Although the SBCs use the similarly quad -A55, but more I/O rich Rockchip RK3568 rather than the Radxa CM3’s RK3566, there is likely a fair degree of software compatibility. Both the SOQuartz and Radxa CM3 mimic the CM4’s 55 x 40 x 4.7mm footprint and 4x M2.5 mounting holes.

SOQuartz with antenna (left) and on DFRobot CM4 Carrier Board
(click images to enlarge)

Like the SOQuartz, the Radxa CM3 has the same dual 100-pin connectors found on the RPi CM4. It also adds a third 100-pin GPIO connector (see farther below). Radxa also revealed two carrier board options for the module: a tiny Radxa E23 board with 2.5GbE and GbE ports and a full-featured Radxa CM3 IO Board, which we will cover in a separate report.


Performance comparisons with the Raspberry Pi CM4 may be highly dependent on the application. The CM4’s quad-core Broadcom BCM2711 uses a Cortex-A72 architecture that is more powerful than the RK3566’s Cortex-A55. However, on the CM4 the SoC is clocked to 1.5GHz rather than up to 2.0GHz on the RK3566. The RK3566 also has the advantage of adding an 0.8-TOPS AI accelerator, and as noted by the CNXSoft post that broke the Radxa CM3 story, the Rockchip SoC supports Armv8 Crypto extensions, which could give it a performance boost over the CM4 on some applications.

The Radxa CM3 also offers faster, optional eMMC. The SOQuartz, meanwhile, may have an edge on some applications if you purchase its optional 128 Mbit SPI flash.

The SOQuartz and Radxa CM3 modules have the advantage of offering native SATA support, multiplexed with the same PCIe Gen2 x1 interface provided by the CM4. Unlike either module, the Radxa CM3 supports USB 3.0, which enables support for 2x SATA, with the second SATA interface multiplexed with USB 3.0. A CM4-based system can use the PCIe interface for SATA but it also requires a separate SATA controller, as with KubeSail’s recent PiBox mini-PC for NAS applications.


The RPi CM4, meanwhile, has the advantage of supplying 2x vs. 1x HDMI 2.0 interfaces. However, the RK3566-based modules add an eDP interface that similarly supports up to 4Kp60.

Although the RPi CM4 is in short supply, there is no indication when the Radxa CM3 will be available. The SOQuartz, meanwhile, is a cutting edge developer release and will likely be sold out before a production release arrives. For some buyers, the SOQuartz and Radxa CM3 will offer an advantage in that they provide more extensive open source resources than Raspberry Pi, including full schematics, which have already been posted by Pine64.


The SOQuartz is “in an early development stage, and therefore only suitable for developers and advanced users wishing to contribute to software development,” says Pine64. Both mainline and Rockchip’s BSP fork of Linux have been booted on the platform, and the module is also supported by an Android 11 SDK for the Quartz64 model A. Yet, despite the fact that the module uses the same processor as the model-A, as well as the upcoming, more feature-rich Quartz64 Model B SBC and PineNote E-Ink notebook, “it will be months before end-users and industry partners can reliably deploy it,” says the company.

The SOQuartz, which we saw on CNXSoft, supplies 16GB to 128GB eMMC vs. 8-32GB on the CM4. Unlike the RPi and Radxa module, there is an option to solder the eMMC on the back, as well as standard, rather than optional, 802.11 b/g/n/ac with Bluetooth 5.0 (Azurewave AW-CM256SM).

The module provides a GbE controller and a USB 2.0 interface. Media I/O includes HDMI 2.0, EDP, 2- and 4-lane MIPI-DSI, and 2- and 4-lane MIPI-DSI. There also appears to be a separate “4Kp60, 10-bit Digital Video” port, although this is perhaps referring to eDP. Pine64 notes that the RK3566’s Mali-G52-2EE GPU uses the open source Panfrost driver.

As noted, the 5V board offers SATA multiplexed with PCIe Gen2 x1. There are also 28 pins of user-available GPIO with 6x UART, 6x I2C, 5x SPI, SDIO, DPI (Parallel RGB), PCM, 2x PWM, and 3x GPCLK.

SOQuartz Model-A Baseboard
(click image to enlarge)

Preliminary specs have been posted for a SOQuartz Model-A Baseboard. The 133 x 80 x 19mm carrier is equipped with a microSD slot, 2x USB 2.0 ports, and 2- and 4-lane MIPI-DSI and -CSI. Other listed specs include a 40-pin GPIO header and a PCIe x1 open-ended slot. The image also shows a GbE port and other features. The wiki also shows images of the SOQuartz loaded onto CM4 carriers from DFRobot and Waveshare.

The DFRobot board appears to be Sourcekit’s PiTray, which we covered back in February. DFRobot also offers a smaller Compute Module 4 IoT Router Carrier Board Mini, which we reported on in March.

The Waveshare boards appeared earlier this year. The Waveshare Compute Module 4 PoE 4G Board is a full-featured carrier with GbE with PoE, M.2 with SIM, PCIe x2, HDMI, USB, and more. The Waveshare Mini Base Board (B) for Raspberry Pi CM4 is a smaller, Raspberry Pi like board that features an M.2 slot with NVMe support.

The SOQuartz is not Pine64’s first compute module. In 2017, it launched the SoPine A64 SODIMM module with an Allwinner A64.

Radxa CM3

The Rock3 Compute Module (Radxa CM3) will be available with Ubuntu 20.04, Debian 10, Buildroot, and Android. The RK3566 will be backed up by 1GB to 8GB LPDDR4. There is also optional eMMC ranging from 8GB to 128GB, and the eMMC access is sped up to 250MB/s rather than 100MB/s on the CM4.

Rock3 Compute Module (Radxa CM3), front and back
(click images to enlarge)

like the SOQuartz, the module offers USB 2.0 and native SATA multiplexed with PCIe. It also provides USB 3.0 via its third 100-pin B2B connector. This speedier USB connection can be configured as a second, albeit slower, SATA interface.

The HDMI 2.0, eDP, and MIPI-CSI support is the same as on the SOQuartz. It differs, however, in offering 2x 4-lane MIPI-DSI (rather than single 2- and 4-lane DSI), one of which can be configured as 4-lane LVDS. Unlike the CM4 and SOQuartz, there is an onboard audio codec and support for audio line-out, I2S, PDM, and a mic array.

The Radxa CM3 provides 50 user-accessible GPIO pins, rather than 28, with features including up to 8x UART, 8x I2C, 4x SPI, and 8x PWM. You also get SDIO 3.0, PCM, and 2x ADC. The 5V module offers optional 802.11b/g/n/ac with BT 5.0. We hope to cover the two Radxa CM3 baseboards soon. Radxa also says the module has been tested on CM4 carriers from MCUZone, Seeed, and Waveshare.

Further information

The SOQuartz module is available to developers for $35 (2GB), $50 (4GB) or $75 (8GB) with WiFi/BT and optional eMMC. No pricing or availability information was provided for the Rock3 Compute Module (Radxa CM3).

More information on the SOQuartz may be found on Pine64’s SOQuartz shopping page and wiki.

More on the Radxa CM3 may be found in Radxa’s announcement, as well as its wiki and GitHub page.

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