HelenOS sources

ETH_100BASE_TX    310 uspace/drv/nic/e1k/e1k.c 	info->ethernet_support[ETH_100M] = ETH_100BASE_TX;
ETH_100BASE_TX   1392 uspace/drv/nic/rtl8139/driver.c 	info->ethernet_support[ETH_100M] = ETH_100BASE_TX;
HelenOS homepage, sources at GitHub