The Nios II processors are three (Fast, Econonomy, and Standard) configurable 32-bit embedded processors for Altera's FPGAs and SoCs.
All cores support up to 256 custom instructions, up to 4 tightly-coupled memories and the configurable debug core.
Recently released are also the Nios II Gen2 cores. These are binary compatible cores with improvements to support additional features. For example, optional full ECC support, 32-bit memory address range, peripheral memory region and improved mul and div instructions.