RSD: a new RISC-V out-of-order superscalar processor

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Susumu Mashimo

Dec 25, 2019, 2:50:39 AM12/25/19
to RISC-V HW Dev
Hi, I would like to share our new RISC-V out-of-order superscalar processor called RSD.

The key features of RSD are:
  • Written in SystemVerilog
  • Run on a Xilinx Zynq FPGA board
  • Can be simulated with Mentor Modelsim/QuestaSim, Verilator, and Vivado
  • Support RV32IM and Zephyr applications
  • 2-fetch front-end and 5-issue back-end pipelines
  • Up to 64 instructions are in-flight
    • These parameters can be configurable
  • A high-speed speculative instruction scheduler with a replay mechanism
  • Speculative OoO load/store execution and dynamic memory disambiguation
  • Non-blocking L1 data cache
  • Support AXI4 bus
  • Support the Konata pipeline visualizer (

We presented RSD in the FPT2019 international conference this year.
You can find the pre-print version of our paper here ('19.pdf).

Ray Van De Walker

Dec 28, 2019, 1:54:03 PM12/28/19
to RISC-V HW Dev



From: Susumu Mashimo <>
to: [hw-dev] RSD: a new RISC-V out-of-order superscalar processor


Hi, I would like to share our new RISC-V out-of-order superscalar processor called RSD.

Akira Tsukamoto

Dec 31, 2019, 4:32:35 AM12/31/19
to Ray Van De Walker,, RISC-V HW Dev

It might be good to request PR here.

Then it should be automatically reflected to the RISC-V Foundation
page bellow with your great out of order soft cpu.

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Susumu Mashimo

Jan 1, 2020, 10:59:52 AM1/1/20
to RISC-V HW Dev,
I opened a PR in the repo you mentioned.
Thank you for your advice.

Susumu Mashimo

Feb 13, 2020, 11:22:54 PM2/13/20
to RISC-V HW Dev
We updated RSD today!
The main changes are:
Currently Synopsys Synplify is required to boot RSD on FPGA, but we plan to make it depend only on Vivado.

2019年12月25日水曜日 16時50分39秒 UTC+9 Susumu Mashimo:

Susumu Mashimo

May 6, 2020, 11:27:11 PM5/6/20
to RISC-V HW Dev
We updated RSD today!
We eliminated the dependency of RSD on Synopsys Synplify.
So now you can try RSD on an FPGA board using only Vivado (free)!

Note that Synplify+Vivado provided better operating frequency compared to Vivado only in our evaluation.
Therefore we still remain the option of using Synplify for users who have the license.
See the wiki page for the detail.

In addition, we added the support of post-synthesis simulation for FPGA.
This simulation is helpful for debugging when RSD runs correctly on the functional simulation but an FPGA.

Dec 9, 2020, 5:17:22 AM12/9/20
to RISC-V HW Dev,
Hi, this is just an FYI but we recently added several features below to RSD.

These features are useful for users who use RSD in a SoC, as RSD can access memory-mapped IO, receive external interrupt, etc.


2020年5月7日木曜日 12:27:11 UTC+9
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