The Raspberry Pi single-board computers or SBCs have long been the darling of makers and tinkerers because of their size and their price. The RPis, however, have also served as the foundation of more formal products that take advantage of the platform more than just the package. For these types of uses, The Raspberry Pi Foundations has provided smaller but also less featured Compute Modules and the latest version based on the RPi 4 shrinks that size down even further with one important consequence.
Calling these watered-down or dumbed-down versions of the Raspberry Pi 4 isn’t exactly fair. Yes, almost all the I/O components have been removed in order to compress the computer into the most compact form possible. Instead of being used out of the box as ready-to-use computers, however, compute modules are instead embedded in larger products, some of them commercially available, that have their own I/O systems anyway.
The Raspberry Pi Compute Module 4 or RPi CM4 is built on the same platform as its namesake, which means using the 64-bit quad-core BCM2711. Like the RPi 4, buyers have a choice of 1, 2, 4, or even 8GB of RAM but, for the first time, there are also options of eMMC storage capacities at 8, 16, or 32GB. Wi-Fi and Bluetooth are also optional.
Another thing that’s new in the CM4 is that the smaller than previous Compute Modules and therefore break compatibility with devices designed around older CMs. I/O signals are now delivered via two high-density perpendicular connectors, one used for power and low-speed interfaces while the other is for high-speed interfaces.
The Raspberry Pi Compute Module 4 now comes in 32 variants, starting at $25. For those who do need all the I/O connectors at least for testing, the Foundation is also selling a matching Compute Module 4 IO Board for $35, without the CM4.