The TN4010 Ethernet controller contains a proprietary microprocessor (known as OptiStrata). The microprocessor manages descriptors to/from the host driver. It manages the DMA parameters for RX and TX as well as some of the offloading functionalities. The firmware is software written by Tehuti Networks and supplied in HEX format as part of the drivers.
The firmware is loaded to the internal memory during controller initialization cycle. It is loaded using special TX Descriptor.
The firmware takes up to 100KB.