Cores available in optimized format are specifically tuned to given processes and are provided as physical silicon layout files. Synthesizable cores are provided at a higher level of abstraction, usually a high level language description of the circuit, and can be quickly adapted to almost any process technology. This will enable companies with existing ASIC designs and external foundry relationships to add MIPS RISC processor capabilities without altering their design and fabrication methodologies. The difference between core formats is determined by the form in which the processor design is delivered to the customer and how that delivery format is created. OEMs could license the CPU, obtain the mask for the processor they wanted and use it to fabricate ICs.
Synthesizable cores deliver the processor design in high level language descriptions of the circuit.
These can be manipulated by an OEM to implement layouts that fit well with existing silicon designs and match well to the OEMs specific process flow. Synthesizable cores provide the greatest flexibility, but require the most effort on the part of the customer. Both custom and optimized cores are delivered as physical layout files that specify the precise silicon geometries for a given process technology. This tailors a given design to a process technology using the physical parameters of that process. The key advantage of optimized cores is that any design can be quickly implemented in a given technology.