M.2 on a Raspberry Pi - the TOFU Compute Module 4 Carrier Board

Ever since the Pi 2 model B went to a 4-core processor, disk IO has often been the primary bottleneck for my Pi projects.

You can use microSD cards, which aren't horrible, but... well, nevermind, they're pretty bad as a primary disk. Or you can plug in a USB 3.0 SSD and get decent speed, but you end up with a cabling mess and lose bandwidth and latency to a USB-to-SATA or USB-to-NVMe adapter.

The Pi 4 actually has an x1 PCI Express gen 2.0 lane, but the USB 3.0 controller chip populates that bus on the model B. The Compute Module 4, however doesn't presume anything—it exposes the PCIe lane directly to any card it plugs into.

TOFU board by Oratek - Raspberry Pi Compute Module 4 Carrier with M.2 slot

And in the case of Oratek's TOFU, it's exposed through an M.2 slot, making this board the first one I've used that can accept native NVMe storage, directly under the Pi:

WiFi 6 is not faster than Ethernet on the Raspberry Pi

I didn't know it at the time, but my results testing the EDUP WiFi 6 card (which uses the Intel AX200 chipset) on the Raspberry Pi in December weren't accurate.

It doesn't get 1.34 gigabits of bandwidth with the Raspberry Pi Compute Module 4 like I stated in my December video, WiFi 6 on the Raspberry Pi CM4 makes it Fly!.

I'm very thorough in my benchmarking, and if there's ever a weird anomaly, I try everything I can to prove or disprove the result before sharing it with anyone.

In this case, since I was chomping at the bit to move on to testing a Rosewill 2.5 gigabit Ethernet card, I didn't spend as much time as I should have re-verifying my results.

MZHOU WiFi Bluetooth M.2 NGFF Adapter Card for PCIe Raspberry Pi Compute Module 4 AX200 Intel 6

How to flash Raspberry Pi OS onto the Compute Module 4 eMMC with usbboot

The Raspberry Pi Compute Module 4 comes in two main flavors: one with built-in eMMC storage, and one without it. If you opt for a Compute Module 4 with built-in eMMC storage, and you want to write a new OS image to the Compute Module, or manually edit files on the boot volume, you can do that just the same as you would a microSD card—but you need to first make the eMMC storage mountable on another computer.

This blog post shows how to mount the eMMC storage on another computer (in my case a Mac, but the process is very similar on Linux), and then how to flash a new OS image to it.

Video Instructions

In addition to the tutorial below, I published a video version of this post covering installation and usage of rpiboot for flashing the eMMC on Windows, Ubuntu, Raspberry Pi OS, or macOS:

External GPUs and the Raspberry Pi Compute Module 4

The Raspberry Pi Compute Module 4 eschews a built-in USB 3.0 controller and exposes a 1x PCI Express lane.

The slightly older Raspberry Pi 4 model B could be hacked to get access to the PCIe lane (sacrificing the VL805 USB 3.0 controller chip in the process), but it was a bit of a delicate operation and only a few daring souls tried it.

Raspberry Pi Compute Module 4 with Zotac Nvidia GeForce GT 710 GPU

Watch this video for more detail about my experience using these GPUs on the CM4:
GPUs on a Raspberry Pi Compute Module 4!

Overclocking the Raspberry Pi Compute Module 4

People have been overclocking Raspberry Pis since the beginning of time, and the Raspberry Pi 4 is no exception.

I wanted to see if the Compute Module 4 (see my full review here) could handle overclocking the same way, and how fast I could get mine to run without crashing.

There's a video version of this blog post, if you'd like to watch that instead:
Raspberry Pi Compute Module 4 OVERCLOCKED.

The Raspberry Pi Compute Module 4 Review

Raspberry Pi Compute Module 4


Six years ago, the Raspberry Pi Foundation introduced the Compute Module: a teensy-tiny version of the popular Raspberry Pi model B board.

Between then and now, there have been multiple revisions to the Compute Module, like the 3+ I used in my Raspberry Pi Cluster YouTube series, but they've all had the same basic form factor and a very limited feature set.

But today, that all changes with the fourth generation of the compute module, the Compute Module 4! Here's a size comparison with the previous-generation Compute Module 3+, some other common Pi models, and an SD and microSD card (remember when the original Pi used a full-size SD card?):