Aeroflex Gaisler provides both a 10/100 (GRETH) and a 10/100/1000 Ethernet MAC (GRETH_GBIT). In addition to supporting the gigabit ethernet mode the 10/100/1000 version also provides a more advanced AHB interface and software offloading capabilities (e.g. checksum offloading) compared to the 10/100 version. The advantage of the 10/100 MAC is the considerably smaller area and easier timing requirements. The 10/100/1000 MAC is only available under a commercial license while the 10/100 version is also available under GPL. More information about each core can be found on their respective pages.