I Just bought a LicheePi 4A RISC-V embedded computer (like a RaspberryPi but with a RISC-V CPU) for $322.68 from Aliexpress (the official site for buying LicheePi devices). Here is the Sipheed web page about it and their other recent offerings [1]. I got the version with 16G of RAM and 128G of storage, I probably don’t need that much storage (I can use NFS or USB) but 16G of RAM is good for VMs. Here is the Wiki about this board [2].
Table of Contents
Configuration
When you get one of these devices you should make setting up ssh server your first priority. I found the HDMI output to be very unreliable. The first monitor I tried was a Samsung 4K monitor dating from when 4K was a new thing, the LicheePi initially refused to operate at a resolution higher than 1024*768 but later on switched to 4K resolution when resuming from screen-blank for no apparent reason (and the window manager didn’t support this properly). On the Dell 4K monitor I use on my main workstation it sometimes refused to talk to it and occasionally worked. I got it running at 1920*1080 without problems and then switched it to 4K and it lost video sync and never talked to that monitor again. On my Desklab portabable 4K monitor I got it to display in 4K resolution but only the top left 1/4 of the screen displayed.
The issues with HDMI monitor support greatly limit the immediate potential for using this as a workstation. It doesn’t make it impossible but would be fiddly at best. It’s quite likely that a future OS update will fix this. But at the moment it’s best used as a server.
The LicheePi has a custom Linux distribution based on Ubuntu so you want too put something like the following in /etc/network/interfaces to make it automatically connect to the ethernet when plugged in:
auto end0 iface end0 inet dhcp
Then to get sshd to start you have to run the following commands to generate ssh host keys that aren’t zero bytes long:
rm /etc/ssh/ssh_host_* systemctl restart ssh.service
It appears to have wifi hardware but the OS doesn’t recognise it. This isn’t a priority for me as I mostly want to use it as a server.
Performance
For the first test of performance I created a 100MB file from /dev/urandom and then tried compressing it on various systems. With zstd -9 it took 16.893 user seconds on the LicheePi4A, 0.428s on my Thinkpad X1 Carbon Gen5 with a i5-6300U CPU (Debian/Unstable), 1.288s on my E5-2696 v3 workstation (Debian/Bookworm), 0.467s on the E5-2696 v3 running Debian/Unstable, 2.067s on a E3-1271 v3 server, and 7.179s on the E3-1271 v3 system emulating a RISC-V system via QEMU running Debian/Unstable.
It’s very impressive that the QEMU emulation is fast enough that emulating a different CPU architecture is only 3.5* slower for this test (or maybe 10* slower if it was running Debian/Unstable on the AMD64 code)! The emulated RISC-V is also more than twice as fast as real RISC-V hardware and probably of comparable speed to real RISC-V hardware when running the same versions (and might be slightly slower if running the same version of zstd) which is a tribute to the quality of emulation.
One performance issue that most people don’t notice is the time taken to negotiate ssh sessions. It’s usually not noticed because the common CPUs have got faster at about the same rate as the algorithms for encryption and authentication have become more complex. On my i5-6300U laptop it takes 0m0.384s to run “ssh -i ~/.ssh/id_ed25519 localhost id” with the below server settings (taken from advice on ssh-audit.com [3] for a secure ssh configuration). On the E3-1271 v3 server it is 0.336s, on the QMU system it is 28.022s, and on the LicheePi it is 0.592s. By this metric the LicheePi is about 80% slower than decent x86 systems and the QEMU emulation of RISC-V is 73* slower than the x86 system it runs on. Does crypto depend on instructions that are difficult to emulate?
HostKey /etc/ssh/ssh_host_ed25519_key KexAlgorithms -ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha256 MACs -umac-64-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
I haven’t yet tested the performance of Ethernet (what routing speed can you get through the 2 gigabit ports?), emmc storage, and USB. At the moment I’ve been focused on using RISC-V as a test and development platform. My conclusion is that I’m glad I don’t plan to compile many kernels or anything large like LibreOffice. But that for typical development that I do it will be quite adequate.
The speed of Chromium seems adequate in basic tests, but the video output hasn’t worked reliably enough to do advanced tests.
Hardware Features
Having two Gigabit Ethernet ports, 4 USB-3 ports, and Wifi on board gives some great options for using this as a router. It’s disappointing that they didn’t go with 2.5Gbit as everyone seems to be doing that nowadays but Gigabit is enough for most things.
Having only a single HDMI port and not supporting USB-C docks (the USB-C port appears to be power only) limits what can be done for workstation use and for controlling displays. I know of people using small ARM computers attached to the back of large TVs for advertising purposes and that isn’t going to be a great option for this.
The CPU and RAM apparently uses a lot of power (which is relative – the entire system draws up to 2A at 5V so the CPU would be something below 5W). To get this working a cooling fan has to be stuck to the CPU and RAM chips via a layer of thermal stuff that resembles a fine sheet of blu-tack in both color and stickyness. I am disappointed that there isn’t any more solid form of construction, to mount this on a wall or ceiling some extra hardware would be needed to secure this. Also if they just had a really big copper heatsink I think that would be better. 80386 CPUs with similar TDP were able to run without a fan.
I wonder how things would work with all USB ports in use. It’s expected that a USB port can supply a minimum of 2.5W which means that all the ports could require 10W if they were active. Presumably something significantly less than 5W is available for the USB ports.
Other Devices
Sipheed has a range of other devices in the works. They currently sell the LicheeCluster4A which support 7 compute modules for a cluster in a box. This has some interesting potential for testing and demonstrating cluster software but you could probably buy an AMD64 system with more compute power for less money. The Lichee Console 4A is a tiny laptop which could be useful for people who like the 7″ laptop form factor, unfortunately it only has a 1280*800 display if it had the same resolution display as a typical 7″ phone I would have bought one.
The next device that appeals to me is the soon to be released Lichee Pad 4A which is a 10.1″ tablet with 1920*1200 display, Wifi6, Bluetooth 5.4, and 16G of RAM. It also has 1 USB-C connection, 2*USB-3 sockets, and support for an external card with 2*Gigabit ethernet. It’s a tablet as a “laptop without keyboard” instead of the more common “larger phone” design model.
They are also about to release the LicheePadMax4A which is similar to the other tablet but with a 14″ 2240*1400 display and which ships with a keyboard to make it essentially a laptop with detachable keyboard.
Conclusion
At this time I wouldn’t recommend that this device be used as a workstation or laptop, although the people who want to do such things will probably do it anyway regardless of my recommendations. I think it will be very useful as a test system for RISC-V development. I have some friends who are interested in this sort of thing and I can give them VMs.
It is a bit expensive. The Sipheed web site boasts about the LicheePi4 being faster than the RaspberryPi4, but it’s not a lot faster and the RaspberryPi4 is much cheaper ($127 or $129 for one with 8G of RAM). The RaspberryPi4 has two HDMI ports but a limit of 8G of RAM while the LicheePi has up to 16G of RAM and two Gigabit Ethernet ports but only a single HDMI port. It seems that the RaspberryPi4 might win if you want a cheap low power desktop system.
At this time I think the reason for this device is testing out RISC-V as an alternative to the AMD64 and ARM64 architectures. An open CPU architecture goes well with free software, but it isn’t just people who are into FOSS who are testing such things. I know some corporations are trying out RISC-V as a way of getting other options for embedded systems that don’t involve paying monopolists.
The Lichee Console 4A is probably a usable tiny laptop if the resolution is sufficient for your needs. As an aside I predict that the tiny laptop or pocket computer segment will take off in the near future. There are some AMD64 systems the size of a phone but thicker that run Windows and go for reasonable prices on AliExpress. Hopefully in the near future this device will have better video drivers and be usable as a small and quiet workstation.
I won’t rule out the possibility of making this my main workstation in the not too distant future, all it needs is reliable 4K display and the ability to decode 4K video. It’s performance for web browsing and as an ssh client seems adequate, and that’s what matters for my workstation use. But for the moment it’s just for server use.
I don’t think this processor supports virtualization, there is no “H” in the instruction set “RV64GCV” (see wikipedia for a list). I haven’t seen one that supports it (or crypto extensions) yet …
https://en.wikipedia.org/wiki/RISC-V
processor : 0
hart : 0
isa : rv64imafdcvsu
mmu : sv39
cpu-freq : 1.848Ghz
cpu-icache : 64KB
cpu-dcache : 64KB
cpu-l2cache : 1MB
cpu-tlb : 1024 4-ways
cpu-cacheline : 64Bytes
cpu-vector : 0.7.1
Does this mean:
Base integer, multiplication/division, atomic, single/double float, compressed, vector, supervisor, and whatever U might stand for?
The C910 core is a RV64GCV, so it’s RISC-V 64 bit, base instruction set group “G” (IMAFD: base ISA, multiplication/division, atomic, single/double float), “C” compressed and “V” vector.
S (kernel mode, probably included in “I” “not embedded”) and U (unallocated, maybe user mode), from a quick search, looks like an idiosyncrasy of the vendor kernel.