anttilukats / f32c

f32c

f32c is a retargetable 32-bit scalar pipelined processor core which can execute subsets of either RISC-V or MIPS instruction sets. It is implemented in parametrized VHDL which permits synthesis with different area / speed tradeoffs, and includes a branch predictor, exception handling control block, and optional direct-mapped caches.

In synthetic integer benchmarks the core yields 3.06 CoreMark/MHz and 1.63 DMIPS/MHz (1.81 DMIPS/MHz with function inlining). A performance-tuned f32c SoC which includes a timer and a UART occupies only 1048 6-input LUTs, while still being able to execute gcc-generated code when synthesized in the most compact configuration which consumes just 697 (649 logic plus 48 memory) LUTs.

Configurable options include:

C_arch               RISC-V or MIPS ISA
C_big_endian         bus endianess
C_mult_enable        synthesize multipler unit
C_branch_likely      support branch delay slot annulling
C_sign_extend        support sign extension instructions
C_movn_movz          support conditional move instructions
C_ll_sc              support atomic read-modify-write constructs
C_branch_prediction  synthesize branch predictor
C_bp_global_depth    global branch history trace size
C_result_forwarding  synthesize result bypasses
C_load_aligner 	     synthesize load aligner
C_full_shifter 	     pipelined instead of iterative shifer
C_debug              synthesize single-stepping debug module

The RTL code also includes modules such as a multi-port SRAM controller, video framebuffer with PAL modulator, SPI, UART, PCM audio, GPIO, PWM outputs and a timer, as well as glue logic tailored for numerous popular FPGA development boards from various manufacturers.

Pre-compiled gcc-based toolchains for Windows, OS-X and Linux can be found at the FPGArduino page, together with pre-built demo bitstreams for various Xilinx, Altera and Lattice FPGAs, and with further instructions on how to compile RISC-V / MIPS executables using the Arduino IDE.

All VHDL modules are BSD licensed. The majority of software libraries are borrowed from FreeBSD, while some originate from other projects and may bear an MIT-style license.