Author | Elektor Lab Mathias Claussen

Translator | He Mu

The all-new Raspberry Pi (Pi) 4 has finally been released! The release of Raspberry Pi 4 brings many changes we have been looking forward to for a long time. Let’s personally evaluate the new hardware and summarize our first impressions. Previously, the changes in each generation of Raspberry Pi were not significant. The update from Raspberry Pi 2 to 3 was a good one, but the Raspberry Pi 3 B+ had only superficial changes compared to the 3B. After the release of Raspberry Pi 3 B+, other competitors released more powerful and feature-rich hardware, such as those including USB 3.0 and native Ethernet. Under the premise of keeping the appearance as similar as possible to previous models, the new Raspberry Pi 4 had to innovate in hardware. Figures 1 and 2 show the details of the hardware. After introducing the hardware, we will discuss the software.

Figure 1

Figure 2

You will also notice two blue USB 3.0 ports and native Ethernet, which solve all the problems of transferring data from large-capacity storage/network. The Raspberry Pi is equipped with the BMC2711 SoC (see Figure 3), which has four Cortex-A72 cores with a maximum frequency of 1.5GHz and supports up to 4GB of memory. Compared to the previous Cortex-A53, the new hardware requires a larger power input to achieve higher performance, which can be felt even in common desktop applications with faster responses. Additionally, the new changes also support 4K output and 4K HEVC 60 fps decoding with VideoCore VI. The SoC itself does not have a fan or heatsink, similar to previous versions, so the Raspberry Pi 4 does not produce much noise during operation. The thermal imaging effects shown later in this article demonstrate the state of the Raspberry Pi 4 in operation. The new SoC presents different power requirements, changing from the previous 5V 2A (3B+ is 2.5A) to the recommended USB-C 5V 3A input, which raises the power to 15W. In addition to the CPU, there are several new components on the board.

Figure 3

Figures 4 and 5 show the gigabit Ethernet interface (BCM54213PE) and USB controller (VLIVL805-Q6), respectively. Looking at the controller’s data, we find that the controller does not use the USB 3.0 upstream line but connects directly to PCI-E 2.0 (backward compatible with PCI-E 1.0). Therefore, the transmission rate will be very considerable. In terms of wireless communication, Bluetooth has been upgraded to version 5.0, and WiFi supports 2.4GHz/5GHz 802.11AC. We will introduce more details later.

Figure 4

Figure 5

The RCA interface (for connecting composite video), display connector, and camera interface have been retained. The 40-pin PCB array has also been retained, allowing us to install expansion boards (HAT) as before.

Next, we will introduce the software support for Raspberry Pi 4. It is important to remind readers that the Alpha test image we used may have missing features. With the release of Raspberry Pi 2, 3, 3 B+, and Zero W, the software has been continuously improving.

The two micro-HDMI interfaces allow us to connect two high-definition displays to the Raspberry Pi 4 simultaneously. During testing, we could see the extended desktop on both screens. We also tried connecting the 10-inch display from Elektor Lab as a second screen but were unsuccessful. When using two 4K screens, the frame rate can reach 30 fps, while connecting only one 4K screen can achieve a maximum of 60 fps. So what can you do with two screens? You can play a video on one screen while browsing the web on the other, or even run some 3D games. In terms of video playback capability, we used VLC to play the video “Big Hero 6” in both 1080p/60fps and 4K/60fps modes. In 1080p mode, we played in windowed mode, and the playback was mediocre with high CPU usage. In fullscreen mode, the CPU load decreased, and the video played smoothly. We attempted to play multiple videos on the screen, but VLC reported an error. Clearly, the video decoder can only decode one video stream. When playing 4K H.264 video on a 1080p display, VLC only produced sound without video, because only H.265 4K video can be decoded. When playing videos from libde265.org, we only saw a black screen with high CPU load, indicating that hardware decoding did not occur properly. 4K video should be supported, so we believe there is a driver issue. Additionally, due to changes in the decoding stack, omxplayer cannot access the hardware properly, thus failing to play any video.

After testing with VLC, we considered trying Kodi. Unfortunately, most video-related software has yet to be updated for the new hardware, and older versions in the Raspbian software repository cannot use hardware acceleration on Raspberry Pi 4.

Many of us have probably forgotten the original USB 2.0 and the not-so-pleasant connection to the SoC. Now, the two blue interfaces and the new USB controller announce that we have finally entered the USB 3.0 era (see Figure 6). The Ethernet interface is no longer connected via USB but connects directly to the SoC. These changes allow for faster speeds for USB devices and improved network speeds.

Figure 6

Now that we have USB 3.0 and gigabit Ethernet, let’s conduct some practical performance tests. Ideally, 1000Mbps means a transfer rate of 125MBps, which is sufficient to build a home network storage system. In our tests, we used SAMBA (Windows file sharing on Linux), which supports three operating systems and is common network sharing software. We selected Kingston’s DataTraveler 100 32GB flash drive as the storage medium. The second storage option was to create a 1.2G RAM disk directly in memory using the command:

sudo mount -t tmpfs -o size=1200M none /ramdisk

After configuring SAMBA, we tested with two files from http://bbb3d.renderfarming.net/download.html (total size 1004968kB). We had already downloaded these two files in the previous video playback test. First, we tested the time to copy the files to the USB flash drive, then tested the time to copy to the RAM disk (removing the impact of slow target storage writes). The script measured the time for the first copy at 9.3 seconds, meaning 108.05MB per second, reaching the flash drive’s limit. The speed of the second copy improved because the RAM acted as a cache. Compared to the Raspberry Pi 3B+, this speed is much faster because the maximum speed of USB 2.0 is only 50MB per second. On Raspberry Pi 3 B+, USB and Ethernet had to share bandwidth. The speed of downloading from a Windows 10 SMB file sharing server with an SSD to the RAM disk reached 102MB per second, which is close to the theoretical limit of 1Gbps when considering SMB protocol overhead. The final test was to copy from the USB flash drive, which theoretically can read at over 100MB per second, with actual results of 98MB per second. As a small and relatively inexpensive file server, the performance of the Raspberry Pi is commendable.

To reduce electromagnetic interference, the WiFi chip on the Raspberry Pi 3 B+ was hidden under a metal cover (see Figure 7), and the layout of Raspberry Pi 4 is similar. Next, let’s quickly test the WiFi functionality.

Figure 7

We tested the data transfer from a Windows 10 computer to the Raspberry Pi 4’s RAM disk. First, we disconnected the LAN and connected to the 2.4GHz WiFi. Raspberry Pi 4 could connect at a maximum speed of 150Mbps with our test access point (maximum connection speed of 300Mbps). During the test, the Raspberry Pi 4 was 10 meters away from the access point with no obstacles blocking (real-world conditions are rarely this ideal). We tested transferring the same data (1004968KB), and the transfer time was 159 seconds. 6.32MB per second is a decent rate. The performance on 5GHz should be better, right? Indeed, it is. However, the Raspberry Pi can only connect to 5GHz access points with channels less than 64. The 200Mbps communication rate of the Raspberry Pi achieved a transfer speed of 7.17MB per second. This speed is sufficient for video watching but clearly not enough for the Raspberry Pi to act as an access point.

Finally, there is Bluetooth. The performance of Bluetooth is similar to that on general Linux. Currently, we do not have any Bluetooth 5.0 devices, and we will conduct further tests when we have devices.

The maximum frequency of each CPU core is 1.5 GHz, which is 100MHz faster than Raspberry Pi 3 B+, a 7.1% increase. While this may not sound like much, the processor has become a Cortex-A72 that prioritizes performance, which elevates the performance of Raspberry Pi 4 to a new level. We used the following sysbench command to test single-core performance:

sysbench -test=cpu run

This test took 121.35 seconds for Raspberry Pi 3 B+, while Raspberry Pi 4 only took 92.78 seconds, 30% faster than the former. Running the test on all CPU cores, Raspberry Pi 3 B+ took 34.54 seconds, while Raspberry Pi 4 took 23.25 seconds, showing a significant speed improvement with the new core.

The increase in CPU speed has raised the overall power consumption of the system. From Figures 8 and 9, we can see that Raspberry Pi 4 runs hotter than 3 B+. Under some load, the temperature becomes noticeably hot, with a maximum observed temperature of 68℃, and several hotspots near the CPU reaching 55℃. Clearly, we need to make some cooling arrangements. The software we are running is a test version, so the heat situation should improve at the time of release. The performance-to-power ratio of Cortex-A72 means that considerable heat will be dissipated during actual use. From the thermal imaging, we can see that the metal cover over the CPU and wireless module is dark in color, but in reality, their temperatures are not low. In fact, it is not a good idea to touch the CPU of Raspberry Pi 4 while it is running. Another hotspot on the circuit board is the USB 3.0 controller, and it is also best not to touch it with bare hands.

Figure 8

Figure 9

Compared to Raspberry Pi 3 B+, even when idle on the desktop, Raspberry Pi 4 is noticeably hotter. Raspberry Pi 4 needs to optimize its power management, but this should improve at the time of the official release. Figures 10 and 11 show the temperatures of Raspberry Pi 3 B+ and Raspberry Pi 4 when idle. In Figure 11, the left side shows the lower temperature of Raspberry Pi 3 B+, while the right side shows the brighter (hotter) Raspberry Pi 4.

Figure 10

Figure 11

Therefore, where you place your Raspberry Pi 4 also becomes an issue. Previously, you could put the Raspberry Pi in a corner, but now it needs some ventilation to avoid overheating. The heat emitted from Raspberry Pi 4 also indicates a relatively high power consumption. So how much power does Raspberry Pi 4 need? We compared power consumption under four loads: idle, playing video, running CPU benchmark tests, and running supertuxkart at 720p. In all tests, we used Raspbian Alpha and connected only one screen.

· Idle on desktop: 2.8W at 5V.

· Playing 1080p “Big Hero 6” video: about 3W in fullscreen, about 4W in windowed mode.

· Running supertuxkart at 720p: about 5W in game.

· Running sysbench: 3.9W for single core, 5.2W for multi-core.

As power consumption increases, so does heat dissipation. If the system is heavily loaded, it is best to ensure airflow around the system. Additionally, the network/USB interfaces can become very hot, so the USB controller and network/WiFi parts will require extra current when transferring data.

A Raspberry Pi 4 running continuously for a year will consume 24.6 kilowatt-hours of power when idle, and the more load it has, the more energy it will consume. You get more computing power, but you also have to deal with more heat, especially after installing expansion boards. The increased memory makes it possible to run virtual machines on Raspberry Pi 4, such as running multiple web servers, MQTT brokers, or encrypted file storage. Of course, we need time to test such applications.

Previous Raspberry Pi models were unable to use 3D acceleration in desktop systems, but the Raspberry Pi 4 and VideoCore VI’s graphics driver solve this issue. In windowed mode on the desktop, 3D acceleration is finally available! Running supertuxkart on Raspberry Pi 3 B+ required a lot of preparation, and even then it might not succeed, but Raspberry Pi 4 can easily run such applications.

Raspberry Pi 4 can quickly start games, achieving an average of 40 frames per second at a resolution of 1024×768 with 3-level effects settings. The frame rate drops to 29 frames per second at 720p, but the game is still playable—this is a significant improvement compared to Raspberry Pi 3 B+. This article has not yet tested running N64 and PS1 emulators on Raspberry Pi 4, but we can confidently say that Raspberry Pi 4’s performance will be better than previous versions.

Figure 12

If you already own an older version of Raspberry Pi or want to use existing expansion boards, you may naturally ask: Can existing expansion boards be used with Raspberry Pi 4? The answer is yes! Of course, connecting a TFT display to the HDMI interface requires new cables.

The support for connecting cameras and displays is basically the same as Raspberry Pi 3 B+, and the 40-pin array on one side of the circuit board has not changed. We can connect expansion boards like StromPi V3 as before. The 3A current means we can easily install StromPi on Raspberry Pi 4. The expansion version of Power over Ethernet (PoE) is not entirely suitable for Raspberry Pi 4 because it can only provide 2.5A of current, so we have encountered many difficulties in previous PoE experiments and have not conducted experiments yet. We will test connecting a 3.5-inch LCD display (TFT) to the Raspberry Pi, as well as installing the Raspberry Pi Foundation’s 7-inch touchscreen on the display connector.

The testing of the Raspberry Pi 4 display interface did not go smoothly; the display showed nothing, and the hardware was not detected. We can only assume that subsequent software patches will resolve this issue. The directly connected 3.5-inch TFT display was detected after standard configuration steps, but if the display content is directed to the screen, the system hangs during boot. This indicates that the software related to display has undergone significant changes compared to before, and the test version software is clearly not ready. Considering that the test version software likely has many issues, we did not conduct further tests with the camera connection and will do so after the official version image is released.

In terms of I/O, the performance of the Serial Peripheral Interface (SPI) and Inter-Integrated Circuit (I²C) is normal, and General Purpose I/O (GPIO) is the same. Software you used in previous Raspberry Pi models should run on Raspberry Pi 4. More adjustments should be made to the software before the official release.

We conducted basic tests on performance, power consumption, and 3D gaming on Raspberry Pi 4. We used preview version software, and many improvements should be made before the official release. Video-related software like openelec still needs some time to adjust for Raspberry Pi 4, but we believe it will eventually be usable on Raspberry Pi 4.

We finally got the long-awaited upgrade: faster USB/network and more RAM. Correspondingly, there is a certain cost: first in price, then reflected in power consumption. The entry-level version with 1GB of RAM is priced similarly to Raspberry Pi 3 B+, and more RAM means higher power consumption and more heat dissipation. Your projects may require more RAM, higher power, more displays, or 4K resolution, and you may also want to use lower power consumption versions for long-term use. We must say we love the increased RAM, USB 3.0 makes data transfer easier, and support for dual displays and 4K resolution allows Raspberry Pi 4 to serve as a thin client, small entertainment machine, living room assistant, or even a small office computer.

Raspberry Pi 4 is a significant step forward, but several issues still plague the industrial applications of Raspberry Pi. First, the microSD card used for storage may fail during operation if not optimized after some time. If Raspberry Pi had a SATA interface, it could solve this issue. Besides storage, heat dissipation is also a problem, and Raspberry Pi 4 has a more pronounced issue than its predecessor. Although 4GB of RAM can alleviate the pressure on SD card storage to some extent, if the operating environment is harsh or difficult to access, Raspberry Pi 4 is not a good choice. If you need to build digital advertising, information systems, and multimedia applications, you will surely look forward to the arrival of Raspberry Pi 4.

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