SoomRV

Description

SoomRV is a simple superscalar out-of-order RISC-V core able to execute up to 4 instructions per cycle and capable of booting Linux. Check the latest CI logs to see a Linux boot log!

For running SoomRV on FPGA, have a look at the SoomRV-Arty Repo.

Basic Architecture

Sample strcmp Execution (visualized using Konata)

Features

• RV32IMAC+ Instruction Set
• 4-wide superscalar OoO Execution (tag-indexed register file, load after issue)
• Implements RISC-V Privileged Spec (M/S/U mode, virtual memory, boots Linux)
• IFetch: 16 byte fetch, TAGE direction predictor, recovering return stack
• Memory: 2 loads per cycle, VIPT cache, late store data gathering, through-memory dependency tracking
• Default configuration scores 5.42 CoreMark/MHz and 4.0 to 11.8 DMIPS/MHz depending on compiler flags (see CI).

Simulating

1. Install the RV32 Linux Toolchain as well as Verilator (at least version 5.0).
2. Run make setup to build submodules.
3. Run make to build a binary with Verilator (alternatively, make trace will also generate VCD traces).
4. To run bare-metal code, use ./obj_dir/VTop <assembly file> or <baremetal elf file>. For example, run ./obj_dir/VTop test_programs/dhry_1.s to run Dhrystone. Optionally add --perfc to print out perf counters, or -x <start_time> to specify when to enable tracing (-x0 for tracing from start).
5. To run Linux, use ./obj_dir/VTop --perfc --device-tree=test_programs/linux/device_tree.dtb test_programs/linux/linux_image.elf (or make linux for a full build). Log in as root, no password. Building Linux and booting it in simulation takes at least a few hours!

Console

The console input is line-buffered for easier input at low simulation speed. Within Linux, you will thus see all input lines twice.

Save/Restore (experimental)

While running, the simulator will save its state about once a minute if --backup-file=<NAME>.backup is specified. Simulation can then be restarted at the backup by running ./obj_dir/VTop <NAME>.backup. The file name must end with .backup. If cosim is enabled, a matching .backup_cosim file will be written/read as well.

This is on by default for make linux. To restart a crashed or closed Linux boot at the last checkpoint, use e.g. ./obj_dir/VTop soomrv.backup --backup-file=soomrv2.backup. (There seem to be some spurious segfaults in the Verilator-generated code.)

Documentation

For a general overview of the implementation, see Overview.

License

SoomRV is released under the MIT License. Use of this source code is governed by a MIT-style license that can be found in the LICENSE file.

External Source Code

• riscv-isa-sim (aka Spike): released under the 3-Clause BSD License, used in conjunction with the simulator.
• hardfloat: released under the 3-Clause BSD License.