Soft-Core CPU

A processor built from fabric.

A soft-core CPU is a processor implemented in LUTs/FFs rather than hardened silicon: RISC-V cores (PicoRV32, VexRiscv, NEORV32), AMD's MicroBlaze, Intel's Nios. They run tens to hundreds of MHz — far slower than a hard ARM core — but you can instantiate five of them, glue custom instructions on, or tuck one in a corner for housekeeping.

The complement is the SoC FPGA (Zynq, Cyclone V SoC), which pairs hard ARM cores with fabric. Rule of thumb: hard core for Linux and heavy software, soft core for control sequencing next to your custom logic — often talking through a register map.