Soft core (synthesis)

A soft core is a digital circuit that can be wholly implemented using logic synthesis. It can be implemented via different semiconductor devices containing programmable logic, including both high-end and commodity variations. Many soft cores may be implemented in one FPGA. In those multi-core systems, rarely used resources can be shared between all the cores.
Examples of soft-core implementations are soft microprocessors, graphics chips like AGA or Open Graphics Project, hard disc controllers etc.