On the 24th of June, the Raspberry Pi foundation announced the new Raspberry Pi 4, which brings a huge number of upgrades to the single board computer.
One of the key design elements of the Raspberry Pi has always been its compatibility, both in terms of the software compatibility and the hardware compatibility with accessories and peripherals between generations.
The RPi 4 represents the biggest generational leap between devices, and as a consequence of this, there have been some compatibility concerns.
To recap, the highlights of the new RPi 4 include:
- A 1.5GHz quad-core 64-bit ARM Cortex-A72 CPU (~3× performance)
- 1GB, 2GB, or 4GB of LPDDR4 SDRAM
- Full-throughput Gigabit Ethernet
- Dual-band 802.11ac wireless networking
- Bluetooth 5.0
- Two USB 3.0 and two USB 2.0 ports
- Dual monitor support, at resolutions up to 4K
- VideoCore VI graphics, supporting OpenGL ES 3.x
- 4Kp60 hardware decode of HEVC video
- Complete compatibility with earlier Raspberry Pi products
However, some considerations need to be taken into account. In particular, there are three major design changes that can affect compatibility. The new RPi has now switched to dual micro-HDMI out, the positions of the ports are around the same location as the previous model, but the placement is different, and the cable is completely different. Similarly, the new device is powered by USB-C, which again is the same placement, but a completely different cable. Both of the design changes are a necessity and allow the RPi to stay current with competing single board computers.
The last change, which makes less sense, is the arrangement of the ethernet and USB ports. The device is now upgraded to Gigabit Ethernet, and now uses two USB 3.0 ports, but their arrangement has been switched around with the ethernet on the right-hand side and the USB ports on the left. The company claim this move greatly simplifies PCB routing. The 4-pin Power-over-Ethernet (PoE) connector remains in the same location, so Raspberry Pi 4 remains compatible with the PoE HAT.
Thankfully the Raspberry Pi 40Pin GPIO is built to be backwards compatible, so any GPIO hat you may have bought should be fully compatible with the new computer.
While Raspberry Pi put a focus on compatibility there are always going to be some software issues to start with. The Broadcom chipset that is used has had a huge upgrade going from a Cortex-A53 to Cortex-A72 CPU and VideoCore IV to VideoCore VI graphics, this will, therefore, mean that most software will need to be tweaked to ensure it runs smoothly.
The RPi Foundation has overhauled the Raspbian OS, so new applications should work with a fresh install, unfortunately for most people, at the moment it is not possible to take a microSD from an RPi3 and it work immediately in the RPi4.