The previous model, the Raspberry Pi Compute Module 3 (CM3), had the same 1.2GHz, quad-core Broadcom BCM2837 processor, VideoCore IV GPU and 1GB memory used on the Pi 3 Model B but packed its components into a slimmer and smaller board. Similarly, the Raspberry Pi Compute Module 4 is based on the Raspberry Pi 4 Model B, but in a smaller form factor.
The Compute Module 4 features the same 64-bit 1.5GHz quad-core BCM2711 processor as the Raspberry Pi 4 Model B, and offers key improvements over its compute module predecessors, including faster CPU cores, better multimedia, more interfacing capabilities, a range of RAM densities and a wireless connectivity option.
It's available with 1GB, 2GB, 4GB or 8GB LPDDR4-3200 SDRAM with optional storage of 8GB, 16GB or 32GB eMMC Flash. The wireless option includes 2.4GHz and 5GHz 802.11b/g/n/ac wireless LAN and Bluetooth 5.0. There's also Gigabit Ethernet.
On the video side, there's dual HDMI output, VideoCore VI graphics with OpenGL ES 3.x support, 4Kp60 hardware decode of H.265 (HEVC) video, and 1080p30 hardware encode of H.264 (AVC) video.
Instead of the 40 GPIO pins on the Raspberry Pi 4, the Compute Module 4 features 28 GPIO pins, with up to six UART, six I2C and five SPI connections.
The Compute Module 4 has a different form factor to previous modules, which does break compatibility between them, but it also enables a smaller footprint on the carrier board. The computer measures 55mm × 40mm (2.16 x 1.57 inches).
This design is aimed at developers who will be using the board for industrial and commercial applications. According to the foundation, seven million Raspberry Pi units per year go to this market.
"Where previous modules adopted the JEDEC DDR2 SODIMM mechanical standard, with I/O signals on an edge connector, we now bring I/O signals to two high-density perpendicular connectors (one for power and low-speed interfaces, and one for high-speed interfaces)," said Een Upton, CEO of Raspberry Pi Trading.
With the Compute Module 4, there are now 32 variants of the Raspberry Pi that range from the $25 Lite edition with 1GB RAM and no wireless, to $90 for the variant with 8GB RAM, 32GB Flash and wireless.
There's also a new Compute Module 4 IO Board to accompany the Compute Module. It includes two full-size HDMI ports, a Gigabit Ethernet jack, two USB 2.0 ports, a MicroSD card socket – only for use with Lite, no-eMMC Compute Module 4 variants – PCI Express Gen 2 x1 socket, a HAT footprint with 40-pin GPIO connector and Power over Ethernet (PoE) header, a 12V input via barrel jack that supports up to 26V if PCIe unused, camera and display FPC connectors, and a real-time clock with battery backup.
The IO board costs $35, giving the complete package with a Compute Module a starting price of $60.
There's also a new Compute Module 4 Antenna Kit for those who want more than the on-board PCB antenna. It features a whip antenna, with a bulkhead screw fixture and U.FL connector to attach to the socket on the module.
Here's the Raspberry Pi Foundation's summary of the Raspberry Pi Compute Module 4's specs:
1.5GHz quad-core 64-bit ARM Cortex-A72 CPU
VideoCore VI graphics, supporting OpenGL ES 3.x
4Kp60 hardware decode of H.265 (HEVC) video
1080p60 hardware decode, and 1080p30 hardware encode of H.264 (AVC) video
Dual HDMI interfaces, at resolutions up to 4K
Single-lane PCI Express 2.0 interface
Dual MIPI DSI display, and dual MIPI CSI-2 camera interfaces
1GB, 2GB, 4GB or 8GB LPDDR4-3200 SDRAM
Optional 8GB, 16GB or 32GB eMMC Flash storage
Optional 2.4GHz and 5GHz IEEE 802.11b/g/n/ac wireless LAN and Bluetooth 5.0
Gigabit Ethernet PHY with IEEE 1588 support
28 GPIO pins, with up to 6 × UART, 6 × I2C and 5 × SPI