chisel-template
riscv-boom
| chisel-template | riscv-boom | |
|---|---|---|
| 1 | 12 | |
| 4 | 1,595 | |
| - | 1.6% | |
| 10.0 | 7.2 | |
| about 1 year ago | about 2 months ago | |
| Scala | Scala | |
| BSD 3-clause "New" or "Revised" License | BSD 3-clause "New" or "Revised" License |
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For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
chisel-template
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I see that many open riscv cores use Scala that generate verilog. Is this common practice?
Also it's not hard to start, there is a template provided by Chisel devs at https://github.com/freechipsproject/chisel-template or my own at https://github.com/carlosedp/chisel-template.
riscv-boom
- Is RISC-V ready for HPC? Evaluating the 64-core Sophon SG2042 RISC-V CPU
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Cascade: CPU Fuzzing via Intricate Program Generation
Looks like from Appendix D that only 2 bugs were found in BOOM:
> 1. Inaccurate instruction count when minstret is written by software
I don't know what that means, but having minstret written by software was definitely not something I ever tested. In general, perf counters are likely to be undertested.
> 2. Static rounding is ignored for fdiv.s and fsqrt.s
A mistake was made in only listening to the dynamic rounding mode for the fdiv/sqrt unit. This is one of those bugs that is trivially found if you test for it, but it turns out that no benchmarking ever cared about this and from all of the fuzzers I used when I worked on BOOM, NONE of them hit it (including commercial ones...). Ooops.
Fixed here: https://github.com/riscv-boom/riscv-boom/pull/629/files
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In your opinion, what is the most advanced open source softcore processor?
The two most micro architecturally advanced cores that I know of are BOOM, an out of order RV64GC core with all the features you expect plus sort of weird fancy things like short forward branch predication, and VROOM, another out of order RV64GC core with things like uop fusion and a trace cache.
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PyXHDL - Python Frontend For VHDL And Verilog
it is used in the Berkley Out-of-Order RISC-V processor: https://github.com/riscv-boom/riscv-boom
- Semidynamics Unveils First Customizable RISC-V Cores for End Users
- TechTechPotato (Dr Ian Cutress): "Building High-Performance RISC-V Cores for Everything"
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Open-source RISC-V CPU projects for contribution
SonicBOOM: https://github.com/riscv-boom/riscv-boom
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The Surprising Subtleties of Zeroing a Register
Some cores are open source and you can see for yourself.
Rename logic from BOOM, a RISC-V core written in a DSL embedded in Scala:
https://github.com/riscv-boom/riscv-boom/blob/1ef2bc6f6c98e5...
From RSD, a core designed for FPGAs written in SystemVerilog:
https://github.com/rsd-devel/rsd/blob/master/Processor/Src/R...
And then there's the recently open-sourced XuanTie C910, which contains this Verilog… which is completely unreadable. Seems like it was produced by some kind of code generator that they didn't open-source?
https://github.com/T-head-Semi/openc910/blob/d4a3b947ec9bb8f...
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Anandtech: "IBM Power10 Coming To Market: E1080 for 'Frictionless Hybrid Cloud Experiences'"
We don't have Sifive's specifically but we do have the open source cores they've historically used to design their cores: https://github.com/riscv-boom/riscv-boom https://github.com/chipsalliance/rocket-chip
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Fence instruction implementation in BOOM
If you look at the decoder (https://github.com/riscv-boom/riscv-boom/blob/master/src/main/scala/exu/decode.scala), you can see that the fence instructions are also marked as "unique" instructions. Only one "unique" instruction is allowed in the pipeline at a time.
What are some alternatives?
OpenROAD - OpenROAD's unified application implementing an RTL-to-GDS Flow. Documentation at https://openroad.readthedocs.io/en/latest/
rocket-chip - Rocket Chip Generator
chisel-template - A template project for beginning new Chisel work
openc910 - OpenXuantie - OpenC910 Core
XiangShan - Open-source high-performance RISC-V processor
rsd - RSD: RISC-V Out-of-Order Superscalar Processor
riscv-mini - Simple RISC-V 3-stage Pipeline in Chisel
Cores-VeeR-EL2 - VeeR EL2 Core
Cores-VeeR-EH1 - VeeR EH1 core
SaxonSoc - SoC based on VexRiscv and ICE40 UP5K
chipyard - An Agile RISC-V SoC Design Framework with in-order cores, out-of-order cores, accelerators, and more
pyxhdl - Python Frontend For VHDL And Verilog