HN Explorer

Ask HN: Are there any open source RISC-V processors that I can buy and use?

10 points by applestone ↗ HN
As of now there are some places which offer small RISC-V processers, such as the StarFive JH7110 (used in DeepComputing DC-ROMA), however when I went to the website it said the CPU was proprietary. Are there any fully open source RISC-V CPUs that are not just hardware simulations that I can actually buy?

15 comments

[ 4.5 ms ] story [ 54.9 ms ] thread
[deleted]
(comment deleted)
duskwuff
RP2350 (Raspberry Pi Pico 2) has two Hazard3 cores, which is open-source at: https://github.com/Wren6991/Hazard3
mrlonglong
Just be aware there's no floating point and there's only machine mode, so you can't run a modern operating system on it. It is purely a microcontroller.
brucehoult
Which is exactly what many people want. OP said "small processor"
6SixTy
But then is followed up using the StarFive JH7110 as an example, which is a Linux capable chip with a GPU rather than a microcontroller with neither of those. Given that OP responded to the person giving microcontroller pointers positively, some form of miscommunication is likely here.
applestone
Apologies for the miscommunication, I'm looking for Linux capable chips
6SixTy
There aren't a whole lot of RISC-V processors that abide by the strictest definition of "fully open source" that are that interesting. There's GPU silicon, encode/decode, sometimes a DSP, maybe even random elements like a memory interface that aren't open source. Strip those out and it's just kind of a text mode only computer or micro controller.
camel-cdr
XuanTie open sourced their C910 [1] and C906 core [2], excluding the xtheadvector support. You can get SBCs with them for quite cheap: C910: Lichee Pi 4A, C906: MangoPi Mq pro

How much of the implementation used in actual silicon overlap with their open source cores isn't clear. I was able to figure out where some non-standard CSR bits are located [3].

Personal, I wouldn't recommend buying them, especially not because they are open source. While source code has been published, the source code looks partially generated and at least for a software dev like me, very hard to read.

I would recommend waiting for the RuyiBook [4], which will contain the second generation of the OpenXiangShan core [5], which is developed fully in the open on GitHub. From the information available, it seems likely that it will become available this year and that it would then be the highest performing RISC-V processor generally available. See my old comment for benchmarks I ran in the RTL simulation: https://news.ycombinator.com/item?id=41331786#41331968 The only unfortunate thing it that it will likely lack support for the vector extension.

I hope they follow my suggestion of shipping the processor source code with the default Linux install.

[1] https://github.com/T-head-Semi/openc910

[2] https://github.com/XUANTIE-RV/openc906

[3] https://github.com/camel-cdr/rvv-d1?tab=readme-ov-file#enabl...

[4] https://milkv.io/ruyibook

[5] https://github.com/OpenXiangShan/XiangShan

See also, slides on the XiangShanV2 microarchitecture: https://raw.githubusercontent.com/OpenXiangShan/XiangShan-do...

applestone
Hey, thank you for such a good response
brucehoult
Hopefully the RuyiBook will be great but it's hardly a "small RISC-V processor".

The ~$5 Milk-V Duos are great. Two C906's, one with MMU and vectors etc for running Linux and one without those for "microcontroller" / "real time" tasks.

camel-cdr
Oh, I totally missed the "small" part.
applestone
You provided what I was looking for, bit of a miscommunication of my part, looking for Linux capable chips, able to run normal applications for daily use
ElectRabbit
WCH is quiet famous for their Risc-V microcontrollers.
jononor
What kind of performance level? RISC-V spans from 15 cent microcontrollers with 32 kB of RAM to multi-core systolic arrays with gigabytes of RAM...
applestone
Something you can run Linux on and use for normal things, web browser, text editor, watching youtube, etc