Raspberry Pi 4

The Raspberry Pi 4 uses a Quad-core ARM Cortex-A72 clocked at either 1.5 GHz or 1.8 GHz depending on the revision of the BCM2711 SoC on the board.[5] The older B0 stepping was originally used for the Pi 4, but this was replaced with the newer C0-stepped chip starting in mid-2021. The higher clock rate of the C0 stepping is due to the marginally improved thermals.[6] The processor also contains 32 KB of data L1 cache and 48 KB of instruction L1 cache, alongside 1 MB of shared L2 cache.[5]

The Broadcom BCM2711 SoC features an upgraded GPU compared to previous iterations of Raspberry Pi, going from the VideoCore IV clocked at 400 MHz to the VideoCore VI clocked at 500 MHz. Alongside the faster clock rate, the VideoCore VI also includes its own memory manager, allowing it to access more memory than its predecessor.[5]The VideoCore VI is compliant with OpenGL ES 3.1 and Vulkan 1.2.[7][8]

The Raspberry Pi 4 replaces the 1 GB of LPDDR2 with options for either 1 GB, 2 GB, 4 GB, or 8 GB of 3200 MHz LPDDR4. The 8 GB Pi 4 released a year after the other models.[9][10]

Raspberry Pi 4 with PoE HAT

Numerous improvements were introduced to IO functionality with the Raspberry Pi 4. The total USB bandwidth was upgraded, going from four USB 2.0 ports to two USB 3.0 ports and 2 USB 2.0 ports. A dedicated ethernet controller on the BCM2711 SoC allowed for the addition of gigabit ethernet.[11] The singular full-sized HDMI port on the Raspberry Pi 3 has also been replaced with dual micro-HDMI connectors.[1][12]Bluetooth was upgraded from 4.2 on the Raspberry Pi 3, to 5.0 on the Raspberry Pi 4.[13]The power supply connector also changed from Micro-USB to USB-C.[14] The ethernet port features Power over Ethernet IEEE 802.3af (802.3at Type 1) like the Raspberry Pi 3 Model B+.

Unlike the original Raspberry Pi 4 Model B, the Compute Module 4 uses a pair of 100-pin connectors on the bottom of the board for IO instead of traditional ports. These connectors aren't meant to be accessed directly by the end user; instead, they are meant to interface with a daughter board to provide it's functionality. While the pins on the Compute Module 4 can be used for the same interfaces as other Pi 4 models, the Compute Module 4 exposes the PCIe 2.0 bus that was previously used for USB 3.0. The freeing of the PCIe bus allows designers to use it for other use cases, such as native NVMe storage or faster networking.[18]Models of Compute Module 4 that have an eMMC chip do not have the capability to connect to external eMMC or microSD storage.[19]

The Compute Module 4 IO Board is an official daughter board designed to give Compute Module 4 users easier access to its various interfaces. While the board does feature many of the same ports as the original Pi 4 Model B, the Compute Module 4 IO Board also adds and changes various connectivity options.[21]

The CM4 IO Board exposes the PCI-e 2.0 bus of the Compute Module 4, rather than having the bus directly connect to a USB 3.0 controller. The bus is exposed through a standard 1x PCI-e connector, allowing for the connection of standard PCI-e peripherals such as networking cards, high-speed storage devices, and even allows the possibility of external GPU support.[22]