RiscV

Warning

This page only documents the first generation of RISC-V CPU created in SpinalHDL. This page does not document the VexRiscV CPU, which is the second generation of this CPU and is available here and offers better performance/area/features.

Features

RISC-V CPU

Pipelined on 5 stages (Fetch Decode Execute0 Execute1 WriteBack)
Multiple branch prediction modes : (disable, static or dynamic)
Data path parameterizable between fully bypassed to fully interlocked

Extensions

One cycle multiplication
34 cycle division
Iterative shifter (N shift -> N cycles)
Single cycle shifter
Interruption controller
Debugging module (with JTAG bridge, openOCD port and GDB)
Instruction cache with wrapped burst memory interface, one way
Data cache with instructions to evict/flush the whole cache or a given address, one way

Performance/Area (on cyclone II)

small core -> 846 LE, 0.6 DMIPS/Mhz
debug module (without JTAG) -> 240 LE
JTAG Avalon master -> 238 LE
big core with MUL/DIV/Full shifter/I$/Interrupt/Debug -> 2200 LE, 1.15 DMIPS/Mhz, at least 100 Mhz (with default synthesis option)

Base FPGA project

You can find a DE1-SOC project which integrate two instance of the CPU with MUL/DIV/Full shifter/I$/Interrupt/Debug there :

https://drive.google.com/drive/folders/0B-CqLXDTaMbKNkktb2k3T3lzcUk?usp=sharing

CPU/JTAG/VGA IP are pre-generated. Quartus Prime : 15.1.

How to generate the CPU VHDL

Warning

This avalon version of the CPU isn’t present in recent releases of SpinalHDL. Please consider the VexRiscv instead.

How to debug

You can find the openOCD fork here :

https://github.com/Dolu1990/openocd_riscv

An example target configuration file could be find here :

https://github.com/Dolu1990/openocd_riscv/blob/riscv_spinal/tcl/target/riscv_spinal.cfg

Then you can use the RISCV GDB.

Todo

Documentation
Optimize instruction/data caches FMax by moving line hit condition forward into combinatorial paths.

Contact spinalhdl@gmail.com for more information