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Turing Pi 2 Clusters Four Raspberry Pi CM4s

Written by Eric Brown

Turing Machines Inc., which earlier this month announced a final 1K run of its Turing Pi cluster board, announced a second-gen Turing Pi 2. Due to ship in 2021, the board offers 4x nodes to cluster Raspberry Pi Compute Modules, compared to 7x for the original Turing Pi. The Gen2 design supports the new Raspberry Pi Compute Module 4 and is equipped with additional interfaces, including 2x mini-PCIe and 2x SATA 3.0.

Turing Pi 2 block diagram (left) and Turing Pi 2 in case
(click images to enlarge)

The Turing Pi 2 retains its 170 x 170mm Mini-ITX form factor and features a Layer-2 managed switch with VLAN support. Although there are fewer nodes, clusters will be easier to scale by connecting and forming larger cluster federations, says Turing. Applications include network attached storage, local or edge hosted cloud hosting, cloud-native and CI/CD development for Arm edge infrastructure, and cloud technology education.

Two of the four nodes link to the 2x mini-PCIe Gen 2 slots. The third node links to a dual-port, PCIe-driven SATA III controller. “This allows connecting external SSDs to the cluster and using the network file system within the cluster to access the drives from all nodes,” says Turing. By connecting a network card to the first node via mini-PCIe, you can have a 2.5GbE Ethernet port that can perform as a router for the other nodes, says the company. The mini-PCIe slots will also support 5G modules.

Turing Pi 1

The Turing Pi 2 moves from one GbE port to two, although there are now 4x USB coastline ports instead of eight. As before, there is an HDMI port and an audio jack, as well as a fan header and a 40-pin GPIO assigned to each node.

The preliminary block diagram above shows that the MIPI-DSI interface that was on the original board but removed from the last 1K run has returned, although the CSI camera interface is still missing. Other internal interfaces include I2C, USB, and control panel.

Turing notes that the new cluster management bus can now flash modules directly through all slots. As shown in the illustrations below, the Raspberry Pi CM4 is housed in a heatsink covered chamber. It connects via the CM4’s revised dual 100-pin Hirose low- and high-speed interfaces to an adapter module.

Turing Pi 2 CM4 interface (left) and exploded view with heatsink covered box, RPi CM4, and the Turing Pi CM4 interface module with dual 100-pin connectors
(click images to enlarge)

With the Raspberry Pi CM4, you can load up to 8GB LPDDR4-3200 RAM on each module with up to 32GB eMMC, thereby providing a cluster of up to 32GB RAM and 128GB storage.

The abundance of RAM enables some interesting configurations. For an Arm development workstation, for example, you could run a desktop distribution like Ubuntu Desktop 20.04 LTS while “the remaining 3 nodes can be used for compilation, testing, debugging tasks, and development of cloud-native solutions for ARM clusters,” says Turing.

Because the Turing Pi 2 is architecturally similar to Amazon’s AWS Graviton ArmV8 Neoverse clusters, “you can build images and applications for AWS instances of Graviton 1 and 2, which are known to be much cheaper than x86 instances,” says the company. Turing also notes that “Turing V2 can easily be included in the existing clusters (cloud or on-premises) and shared with other participants using Kubernetes RBAC.”

The Turing Pi 2 debuts a “unified compute module interface” that “will allow connecting compute modules from other manufacturers and also combine different purpose modules to solve specific tasks like machine learning at the edge.” No more details were supplied, but one could imagine interesting applications that mix Raspberry Pi, Nvidia Jetson, or Google Coral modules.

 Raspberry Pi CM4 recap


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The Linux-powered, $25 to $90 Raspberry Pi Compute Module 4 has the same Broadcom BCM2711 SoC with 4x 1.5GHz Cortex-A72 cores that is used on the Raspberry Pi 4. The module ships with 2GB to 8GB LPDDR4-3200 RAM and 0GB to 32GB eMMC. There is a GbE controller with PoE support, optional 802.11ac with BT 5.0, and new support for dual 4K HDMI ports and PCIe 2.0.

Raspberry Pi CM4

The CM4 switches from the SODIMM connector of the RPi CM3+ and CM3 to dual (low speed and high speed) 100-pin, perpendicular Hirose DF40 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. Gumstix, however, has already announced a $30 Uprev adapter board that lets the CM4 run on a CM3 carrier. Gumstix also announced several robotics, camera, and drone carriers for the CM4.

 Further information

The Turing Pi 2 will go on sale in 2021 at an undisclosed price. Turing Machines speculates that due in part to the reduced number of nodes, the Turing Pi 2 will be more affordable than the $189 Turing Pi 1. In addition, customers of the first Turing Pi will receive a 25 percent discount. You can now sign up to be notified of availability. More information may be found in Turing Machines’ announcement and product page.

This article originally appeared on on October 22, 2020.

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Turing Pi 2 Clusters Four Raspberry Pi CM4s

by Eric Brown time to read: 3 min