If I want to do systems research that needs a simple and synthesizable RISC-V design, what are some good options? BOOM seems to be pretty complicated and I don't really need the out-of-order execution.
I also want to be able to run it on a cheap FPGA, something like Artix A7.
This is what the OpenHW Foundaiton is for. Providing well verified cores for people who just need a core. They are based on the original Pulp Cores from the ETH Zürich and Unviersity of Bolongia. See:
RISC-V is still at the point where open-source implementations (in rtl) are faster than purchasable proprietary ones (in silicon).
XiangShan is currently the fastest open-source CPU implementation: https://github.com/OpenXiangShan/XiangShan
uarch slides: https://tutorial.xiangshan.cc/hpca25/slides/20250302-HPCA25-...
uarch slides with WIP features: https://tutorial.xiangshan.cc/micro25/slides/Microarchitectu...
If I want to do systems research that needs a simple and synthesizable RISC-V design, what are some good options? BOOM seems to be pretty complicated and I don't really need the out-of-order execution.
I also want to be able to run it on a cheap FPGA, something like Artix A7.
Rocket-chip is widely used (https://github.com/chipsalliance/rocket-chip). It can fit on smaller FPGAs.
If you want something very tiny and completely understandable, and don't mind that it's 32 bit, then PicoRV32 (https://github.com/YosysHQ/picorv32).
This is what the OpenHW Foundaiton is for. Providing well verified cores for people who just need a core. They are based on the original Pulp Cores from the ETH Zürich and Unviersity of Bolongia. See:
https://openhwfoundation.org/
Or because its part of OpenTitan, Ibex sees a lot of development: https://github.com/lowRISC/ibex
There’s a nice list of open source cores here: https://github.com/suryakantamangaraj/AwesomeRISC-VResources
Try neorv32: https://github.com/stnolting/neorv32
Thanks. Looks good! Are you aware of any 64-bit options?
https://github.com/Wren6991/Hazard3
this one is well tested in real life and works well (it is the RV core in RP2350)
The latest version seems to be Sonic Boom:
https://github.com/riscv-boom/riscv-boom
But this project seems to have stagnated with one significant commit in the last year.