The Raspberry Pi has been extremely successful, and part of that success is due to regular upgrades to deliver more performance and functionality. The Raspberry Pi 4 continues this progression. Of course, there are new features, challenges and some caveats.
Overall, the Raspberry Pi 4 Model B (Fig. 1) delivers the good goods. It’s available from a number of sources like Newark or SparkFun. The module is built around a Broadcom 2711 that’s based on a 1.5-GHz, 64-bit, quad-core Arm Cortex-A72 processor. The processors have a 15-stage pipeline compared to the 8-stage pipeline in the Raspberry Pi 3’s Cortex-A53 SoC.
1. The Raspberry Pi 4 Model B doesn’t come with a heatsink or fan, but it can use one if you’re going to push its performance.
The Raspberry Pi 4’s GPU in this SoC is a VideoCore VI that supports OpenGL ES 1.1, 2.0, and 3.0. The video can drive two 4K UHD displays via micro-HDMI ports. It has H.265 decode (4kp60) and H.264 decode (1080p60) as well as VP9 decoding support. The challenge is making sure the hardware acceleration is used by the software, because the processors aren’t up to doing 4K video in software.
One of the biggest changes is that the boards are available with 1, 2, or 4 GB of LPDDR4 RAM. The higher memory busts the $35 price point, but it’s a greatly anticipated option since earlier devices have been limited by their memory footprint. Just under $60 gets a 4-GB unit.
The other change is the migration away from USB-based Ethernet. It limited the Gigabit Ethernet interface to about 300 Mb/s. The Raspberry Pi 4 has native Gigabit Ethernet support plus Power-over-Ethernet (PoE) support, although the PoE board blocks out the expansion header.
The board comes with a pair of USB 3.0 SuperSpeed ports and a pair of USB 2.0 Hi-Speed ports. There’s a USB Type-C connector, but that’s for power only. More on that later.
In addition to Gigabit Ethernet, the board has dual-band 802.11b/g/n/ac wireless support. It also supports Bluetooth 5.0.
The pair of micro-HDMI connectors isn’t really bad, but they’re annoying since most displays have a regular HDMI connector. This means getting a special cable or a micro-HDMI to HDMI adapter. I picked up a pair of the latter.
My big concern is heat. The board comes without a heatsink and it does run without one. The issue is performance. Though the hardware can throttle back when it gets hot, it sort of defeats the higher-performance features when the chip is running at full tilt.
There have been heatsink and cooling fan options for the Raspberry Pi 3, but the Raspberry Pi 4 takes things to a new level. It’s not surprising that a range of options are available.
Shenzhen Lonten Technology’s Raspberry Pi 4 cooler (Fig. 2) is compact enough to fit inside most cases. Including a fan is almost a requirement, and it means that if a case is used, then it needs to provide ventilation for the fan.
2. Shenzhen Lonten Technology’s heatsink and fan are compact enough so that the system can fit in most Raspberry Pi 4 cases.
C4Labs’ Zebra 4 (Fig. 3) adds a clear case to the mix. It will not accommodate expansion options, but many Raspberry Pi systems are simply used for compute chores with the USB ports or network providing access to peripherals.
3. C4Labs’ Zebra 4 includes a clear plastic case to keep the Raspberry Pi cool.
Seeed’s ICE Tower (Fig. 4) makes the system look more like a compact PC. Actually, performance-wise, the Raspberry Pi 4 can easily work as a PC, and its compact size makes it an option for a multimedia platform.
4. The Seeed ICE Tower can really keep the Raspberry Pi 4 cool, enabling full performance without worrying about the heat level.
I actually used my own heatsink and fans, but would like to try one of the systems designed for the Raspberry Pi 4. These make it easier than leaving the unit on the lab bench like I do.
The system is powered by a 5-V, 3-A USB Type-C power supply that’s not included. The connection isn’t used for communication, so it’s not a fifth USB port. The problem comes in the sensitivity of the Type-C power requirements. This is actually an issue with the design of the board and the implementation on the power supplies on the market. I powered the unit with my PC that has a USB 3 Type-C connection. Of course, I tried it with four other USB Type-C power supplies and batteries and half did not work. I didn’t have the PoE Hat handy, so I didn’t get to try that option.
The other issue is one mentioned earlier. Streaming 4K to two screens sounds great, but it doesn’t work without hardware acceleration and it definitely likes a heatsink and cooling fan. The system works well with dual 4K displays if it’s not streaming video or doing heavy lifting like playing games. And it works fine for editing and other chores where the limiting factor is a person like me with a mouse and keyboard.
Using the Raspberry Pi 4
The system boots from a number of sources; usually it’s a microSD card, though. A 16-GB card can easily handle the NOOBS (New Out Of Box Software) or Raspbian platforms. Both are based on Linux. They can fit in a 4-GB card, but that doesn’t give a lot of working room. MicroSD cards from outfits like Newark come with the operating systems already installed. However, it’s easy enough to download the latest software onto a blank card.
It’s also possible to boot from the USB ports. This can be from a USB hard disk or SSD or a flash stick. I happen to have lots of these handy, so it was easy to check out. It’s not really different than using the MicroSD card, but a USB 3.0 disk will be considerably faster.
A more interesting option is PXE boot via the Gigabit Ethernet interface. I didn’t try it with the board since I would have to set up a PXE boot server. It’s not hard, but you also need to install the Raspberry Pi software on the server. Again, not hard—it just takes a little bit of time. I was debating about setting up a PXE boot server on the Raspberry Pi 3, but that will have to wait.
Raspbian is the OS I tried out and I was impressed with the setup. The setup wizard requires a password, so a bare Raspberry Pi 4 will not be on your network unless you actually work at doing that.
Though the Raspberry Pi 4 makes a decent workstation, its primary role will likely be in embedded systems like robots. The added processing power and GPU support will be useful in these applications, especially as technologies like machine learning are employed. The USB 3.0 support makes it possible to use devices like Intel’s Neural Compute Stick 2.
It was fun to have a snappier version of the Raspberry Pi, and the great memory footprint makes a big difference. It’s likely to be less of an issue for an embedded system where applications may be more static. Still, the lack of expansion beyond 4 GB can be a limiting factor for some applications.
The main attraction for the Raspberry Pi 4 remains the massive peripheral and software options available. It’s a good experimentation and prototyping platform, but the family isn’t necessarily a great fit for moving forward into a product. Broadcom doesn’t sell chips in small quantities.
The Pi Compute modules (Fig. 5) are an option, but one that matches the Raspberry Pi 4-compatible compute module is still in the works. The challenge there will be heat issues. Adding a heatsink and fan to a module can be a challenge.
The Raspberry Pi 4 is sneaking up on the low-end PC market. However, it lacks features like PCI Express and access to NVMe storage. On the flip side, Raspberry Pi continues to do much better in dealing with peripheral options needed in the embedded space. You will be quite pleased with the Raspberry Pi 4 as long as you keep its advantages and limitations in perspective.