neorv32 VS linux-on-litex-vexriscv

How about NEORV32?

GitHub - stnolting/neorv32: 🖥️ A tiny, customizable and highly extensible MCU-class 32-bit RISC-V soft-core CPU and microcontroller-like SoC written in platform-independent VHDL. this one is good but is written in VHDL though

NEORV32 is an open source soft core and very well documented. I would recommend you to take a look at it and play around a bit. And it is certainly possible to have a soft core running on only the PL side without PS interference.

Maybe not a classic (whatever that means...) project, but I am working (together with others) on a RISC-V microcontroller for FPGAs: https://github.com/stnolting/neorv32

With LiteX you can synthesize a VexRiscV processor. You can run Linux on it. The toolchain is pretty easy to use, as long as you use Xilinx Vivado to compile to gateware.

Hello, we are planning to rebuild a computer architectures course at uni and the idea is to teach the basics using the riscv architecture. We are looking for an affordable development board that could be used to demonstrate both bare-metal programming as well as interfacing hardware via mmap from OS to build up the experience with accessing the registers directly, and then introducing virtual memory, memory hierarchy, etc. So far it seems like a best option to utilize some compatible FPGA development board and the litex ( https://github.com/litex-hub/linux-on-litex-vexriscv ) project to achieve the afforementioned. Would you have any comment on that or perhaps some other recommendation for an affordable development board? Thanks for any tips.

The repo below has support for building a 32bit RISC-V CPU for de10nano. It also includes information about booting Linux.

https://github.com/litex-hub/linux-on-litex-vexriscv

The CPU will likely have a clock speed around 100Mhz, far slower than the 1.5Ghz 64bit cores on the VisionFive 2 or Pi4. The FPGA might still be useful if you want to customize the CPU or integrate other custom hardware.

You can run linux even on an entirely open source from hardware to software toolchain: https://github.com/litex-hub/linux-on-litex-vexriscv

On the other hand, if you really want a budget FPGA board under 100 USD that can implement a Linux-capable RISC-V SoC, you will need to implement a simple 32-bit one but indeed possible. See https://github.com/litex-hub/linux-on-litex-vexriscv for instance. You will get additional frequencies (still an order of 100 MHz though), I/O ports and such if you can spend 200 to 300 USD.

An Artix 7 100k (like in the 'big' Arty A7 board) will comfortably fit 4 VexRiscv @ 100 MHz in a Litex SoC with all the bells and whistles; you can already fit a SoC with 2 Vex in the smaller 35k. Running Linux on that is very easy.

Accessibility has improved significantly over the last few years. You can now buy any of the Lattice iCE40 or ECP5 boards from this page and use the yosys open-source workflow to upload real designs to the cores, including soft cores capable of running real, unmodified Linux. These tools are actively developed and are used by the open-source FPGA community at large (with the iCE40 and ECP5 receiving massive upticks in mindshare as a result).