$99 SBC runs Linux on Allwinner D1 with RISC-V RV64 extensions

$99 SBC runs Linux on Allwinner D1 with RISC-V RV64 extensions

May 21, 2021 — by Eric Brown

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[Updated: May 22] —Sipeed has launched a $99 “Nezha” SBC that runs Linux on the 1GHz Allwinner D1 with a RISC-V XuanTie C906 core with RV64 vector extensions. Meanwhile, RVBoards offers an almost identical D1 ref design as the $93 “RVBoards-Nezha.”

Sipeed has gone to Indiegogo to launch the first SBC built around the recently revealed, RISC-V architecture Allwinner D1 SoC. The open-spec, Linux supported Nezha SBC starts at $99. Prices move up to $170 for a fully configured model with touch-panel, mic array, and USB camera add-ons, which are also available separately. Sipeed appears likely to reach its flexible, $10K campaign goal. The company expects to ship starting in June.

RVBoards, a community project from PerXLab, has an almost identical board on sale at TaoBao in China for $93 under the name D1 development board Nezha Quanzhi. It also briefly appeared on AliExpress under the name RVBoards-Nezha before being pulled (see farther below).

Sipeed’s Nezha on Indiegogo (left) and RVBoards-Nezha
(click images to enlarge)

Update: Yesterday’s original version of this story (before we pulled it) incorrectly identified the Indiegogo project as being from RVBoards. RISC-V developer Bruce Hoult informed us of our error, noting that the rival companies “are simply distributing the same manufacturer’s evaluation board made by (or for) Allwinner.”

Meanwhile, Rick Lehrbaum, founder of LinuxGizmos, pointed us to his own Nezha post at HackerBoards, where he correctly identified the Sipeed connection. He also shared a response from Sipeed to his question about the manufacturing source, which stated that Allwinner has built the first boards itself. The next batch is being manufactured by Sipeed for Indiegogo before moving on to TaoBao and Aliexpress. There was no mention of RVBoards.

Here we focus on the Sipeed Nezha on Indiegogo. The RVBoards version (above right) appears to be identical except that it ships with an acrylic shell and a 32GB microSD card instead of 16GB. It also adds a heat sink, light sensor, and atmospheric pressure sensor. It appears to lack the touch-panel and mic array options, although the DSI and mic interfaces are there, but it ships standard with the USB camera. More details may be found in the RVBoards links at the end of the story.

Allwinner D1

When it was revealed last November that Allwinner and Alibaba’s T-head subsidiary were collaborating on an unnamed SoC based on a T-head’s single-core, RISC-V-based XuanTie C906 core, it was expected to arrive first on an unnamed $12.50 Sipeed SBC. Instead after Allwinner announced the D1 SoC on EETimes last month, images and specs began to appear for an Allwinner D1 development board, which is now called the Nezha.

The initial Nezha launch report was from CNXSoft, which also said that a prototype of the $12.50 Sipeed board will soon ship to developers. Hoult tells us the $12.50 board will be released later in the year, delayed due to supply issues. In February, Pine64 revealed plans to develop an under $15 board based on the D1.

Allwinner D1 block diagrams
(click images to enlarge)

The Allwinner D1 builds on the XuanTie C906 core, which has a 5-stage, in-order pipeline with up to 64KB instruction and data cache, interrupt controllers, and a 128-bit AXI 4.0 bus. Allwinner adds a HiFi4 DSP, a G2D 2D accelerator, and video decode/encode. This includes H.265 decode at 1080p@60fps (or 4K@30fps) and JPEG/MJPEG encode (CSI/CVBS) at up to 1080p@60fps. Like other RISC-V SoCs to date, it lacks a 3D GPU.

Bruce Hoult noted that the Nezha board implements the Allwinner D1’s RISC-V standard Vector (RVV) RV64GCV extension. Indeed, Sipeed bills the Nezha as the first mass produced RV64 SBC.

Last month, SiFive announced that its new X280 core IP would implement RV64GCV in a customized variant it calls SiFive Intelligence. The vector extensions can enable on-chip processing of AI/ML tasks, among other uses.

According to Hoult, the Nezha board’s D1 “implements an early draft version (0.7.1) of the RISC-V V extension. There are some major incompatibilities with the 1.0 spec that will be ratified in July or August, but most instructions and opcodes are the same, as is the overall structure of code. I’ve confirmed that a simple (but fast!) vectorized memcpy() is binary compatible between 0.7.1 and 1.0 and many other things will be also. Even when incompatible, the changes required at the assembly language level are minor.”

The up to 1GHz core provides 2.4 DMIPS/MHz (O2) and 3.8 CoreMark/MHz (O3) performance. This compares to 7.1/MHz CoreMark for T-head’s 16-core XuanTie 910 and 5.1/MHz CoreMark for the SiFive U74 IP found on its FU740 SoC and new HiFive Unmatched SBC. The Unmatched board has finally begun shipping to pre-order customers after a five-month delay due to the usual supply issues.

Nezha SBC

The Nezha, which is named after a protective deity in Chinese mythology, has a Raspberry Pi-like 85 x 56mm form factor with a 40-pin GPIO, but no promises of Pi HAT compatibility. The board ships with 1GB DDR3, 256MB NAND, and a microSD slot.

The SBC is further equipped with a GbE port, WiFi/Bluetooth, and a USB 2.0 port that supports an optional, $10, 720p USB camera. There are also dual USB Type-C ports: an OTG port and a port for 5V input.

Nezha rear view (left) and detail view with 40-pin pinout
(click images to enlarge)

The Nezha has an HDMI port and a MIPI-DSI interface with an optional, $50, 8-inch capacitive touch-panel. For audio, there is a 3.5mm audio jack and a mic interface that supports an optional, $17, 6-mic array. The Standard Suit includes a power supply, and cables.

The Nexha will ship with a 16GB microSD card “pre-burned” with a Debian 11 image maintained separately by RVBoards and Sipeed. The board is also available with Allwinner’s OpenWrt-based Tina OS, which is not to be confused with Tina Linux. Mainline Linux and other Linux distros are in progress.

Nezha Full Suit kit
(click image to enlarge)

The Indiegogo page offers instructions to remotely test the board via ssh. RVBoards also notes that the board has been tested for C/C++, JS, WASM, Rust, GoLang, and Python development.

Specifications listed for the Nezha SBC include:

• Processor — Allwinner D1 (1x RISC-V T-Head XuanTie C906 @ 1GHz); HiFi4 DSP, G2D graphics accelerators, etc.
• Memory/storage:
  • 1GB DDR3
  • 256MB SPI NAND flash
  • MicroSD slot
• Networking:
  • GbE port (RTL8211F)
  • 802.11n plus Bluetooth (XR829)
• Media I/O:
  • HDMI 1.4 port @ up to 4Kp30
  • MIPI-DSI with up to 1080p60 with optional 8-inch 1280 x 800 IPS cap touch-panel and holder
  • 3.5mm audio jack
  • Mic FPC connector with optional 6-mic array with 5 ADC keys and 12x serial RGB LEDs
  • Optional 720p USB camera
• Other I/O:
  • USB 2.0 host port
  • USB OTG Type-C port
  • USB OTG Type-C port for 5V/2A input
  • 4-pin UART debug header
  • 40-pin GPIO connector with SPI/UART/IIC/PWM/LEDC/IIS/GPIO
• Other features – Power LED and tri-color user LED; OK and FEL buttons
• Power — 5V/2A input via USB Type-C
• Dimensions — 85 x 56mm (6-layer PCB)
• Operating System — Debian 11 “pre-burned” on 16GB card; Tina OS (OpenWrt); Fedora, Gentoo, and Ubuntu under development

Sipeed’s Nezha

Further information

Sipeed’s Nezha is available on Indiegogo for the next 18 days starting at 768HKD ($99) for the Standard Suit. Other options include a $109 Vision Suit, which adds a camera, as well as a $116 Audio Suit (mic array), a $149 Panel Suit (touch-panel), and the $170 Full Suit (all three options). Shipments begin in early June.

The rival RVBoards-Nezha board using the same reference design is available on TaoBao starting at 599 RMB ($93) and it may return to this AliExpress page. More information may also be found on PerfXLab’s RVBoards D1-Board documentation page and more should eventually appear on the RVBoards website.

More information on the Allwinner D1 may be found on Allwinner’s D1 documentation page and this linux-sunxi page.