The “Nezha” board from the Chinese company RVBoards is probably the first (reasonably) affordable RISC-V single-board computer for Linux. Because the RISC-V calculation core in the system-on-chip Allwinner D1 is compatible with the RV64GC specification. In addition, a 2D graphics processor is built in so that the Nezha can control an HDMI display like a Raspberry Pi.
The other equipment of the Nezha is also similar to an (older) Raspi: 1 GByte RAM, Gigabit Ethernet, USB 2.0, MicroSD card reader, WLAN, USB 2.0 OTG, 5-volt power supply via USB-C and 40-pin pin header with interfaces such as I2C, SPI, GPIO. An integrated USB-to-serial converter enables access to a text console.
The $ 99 “Nezha Basic” offer includes a MicroSD card with 32 GB capacity and a pre-installed Debian installation, which makes commissioning fairly easy. The RISC-V variant of Debian was specially adapted for the Nezha by RVBoards.
By default, the preinstalled “riscv64” Debian (Kernel 5.4) starts an LXDE desktop. The only processor core with a clock frequency of only 1 GHz has to struggle with this, the surface reacts very slowly. HDMI output, USB 2.0 and Gigabit Ethernet work without any further configuration.
Contrary to what has been documented, the default root password is not “rvboards”, but “root”. The system receives software updates as standard via an unencrypted connection from a server in the domain of the RVBoards parent company PerfXlab (http://mirrors.perfxlab.cn/debian-ports/). The preinstalled Midori browser only displays websites that are kept simple, such as Wikipedia.
Weak computing power
Linux recognizes the type of RISC-V core as “rv64imafdcvu”, so it is RV64GC compatible (IMAFDC) and also has vector extensions (V). The “T-Head” chip division of the Chinese trading giant Alibaba developed the core; it is a XuanTie E906. Allwinner combines it in the D1 chip with a DDR3 memory controller, a DSP (Cadence Tensilica HiFi 4) as well as with numerous interface controllers (SPI, I2C, USB 2.0, Gigabit Ethernet) and a 2D graphics engine. The latter connects to the HDMI output. The chip contains video decoders and encoders, which Allwiner also integrates in other in-house SoCs.
Graphics drivers that use hardware acceleration functions don’t seem to exist yet. The RISC-V core only clocks at 1 GHz and can only use 1 GB of RAM.
Two small benchmarks, namely from openssl (
openssl speed aes-128-cbc) and 7-Zip (
7z b) show that the Allwinner D1 only provides a fraction of the computing power of the Broadcom BCM2711 of a Raspberry Pi 4. With openssl, which only uses a single CPU core in this benchmark (the BCM2711 has four), the D1 achieves around 13 percent of the performance of an ARM Cortex-A72 with 1.8 GHz. With 7-zip, the D1’s performance is only around 6.5 percent of that of the BCM2711, so the latter is more than 15 times as fast.
Unfortunately, you have to gather information about the RVBoard Nezha on several websites and in a forum, sometimes at Allwinner, partly at RVBoards. RVBoards belongs to the company PerfXlab and has cooperated with Allwinner in the development of the Nezha. The board was funded through an Indiegogo campaign, but is also available through AliExpress – a division of Alibaba. Allwinner maintains with Tina Linux aw-ol.com (AWOL) its own Linux distribution as well as an SDK for the D1. The RVBoards Nezha is primarily intended for developers of RISC-V-Linux.
Further information on RVBoards Nezha can be found in c’t 17/2021, which will be published on July 31.